There's the essay, it's from 2001, about the Force in Episode I.
The idea of the Unifying Force is essentially a Taoist influence on the Force; especially the idea that the dark side is equally as necessary as the light. This is in contrast to the Manichean dualism that originated in the Expanded Universe out of the original trilogy, but given Yoda's Taoist teachings in The Empire Strikes Back, I believe that arises out of a projection of Manichean dualism onto the source material rather than it already existing there, at least to the extent that the Expanded Universe took from it. The dark side is definitely more corresponding with evil than yin yang in Tao, for instance.
I also believe that the Unifying Force as a concept is inherent to the Force as depicted in the original trilogy. The Unifying Force is the Force. It's an energy field that surrounds and binds all living things. The dark side of the Force is a side of the Force, but "the Force is what gives a Jedi his power," not the "light side" of the Force. The dark side is only negative when used out of balance within the Force, or in excess.
As for the quotes, I'll go to Vergere's speech about the dark side in Traitor:
JACEN: "What do you mean? I can feel the dark side here. I touched the dark side, and it, and it, it touched me..."
VERGERE: "No. What you feel is the Force. This is the shameful secret of the Jedi: There is no dark side."
JACEN: "Vergere, I know better. What do you think just happened here?"
VERGERE: "The Force is one, Jacen Solo. The Force is everything, and everything is the Force. I've told you already: the Force does not take sides. The Force does not even have sides."
JACEN: "That's not true! It isn't... It's a lie..."
VERGERE: "No. Search your feelings. You know this to be true. The Force is one. Light and dark are no more than nomenclature: words that describe how little we understand. What you call the dark side is the raw, unrestrained Force itself: you call the dark side what you find when you give yourself over wholly to the Force. To be a Jedi is to control your passion... but Jedi control limits your power. Greatness -- true greatness of any kind -- requires the surrender of control. Passion that is guided, not walled away. Leave your limits behind."
When taken at face value, this sounds like Vergere is trying to fool Jacen into using the dark side freely, because if you don't control your passion and surrender yourself to it, especially if that passion is anger, you're becoming like Luke did on the second Death Star when he cut off Vader's hand. But Vergere's talking about the Unifying Force here, and is trying to impress upon Jacen the holistic nature of the Force itself. It does have sides. It encompasses everything, so those things associated with the light and dark sides are encompassed within the Force.
But it's also true that the Force doesn't take sides. The will of the Force isn't beholden to the light or dark sides of it. This is clear through the film saga itself.
As for the idea of surrender, this is echoed by Sekot, as I previously posted:
"Jacen, to tap deeply into the Unifying Force, we will have to surrender our desire to control events. We will have to unbridle ourselves of words and of thinking, because thoughts, too, are born of the physical world. We must refrain from analyzing the Force, and simply allow the Force to guide us. Our relationship with the Force must be impeccable, without the need to be supported by words or reason. We must carry out the commands of the Force as if they were beyond appeal. And we must do what must be done, no matter who attempts to stand in our way."
The idea even goes as far back as to Shield of Lies, in which Luke demonstrates a similar understanding of the Force:
"He then took advantage of the open space inside the bay to work his first complete set of Jedi training drills since leaving Coruscant. Working both with and without his lightsaber, he patiently went through the complex exercises which brought him to a profound state of restful clarity. It was in this state that he felt most keenly the truth and the wisdom of the simple words: There is no emotion; there is peace. There is no ignorance; there is knowledge. There is no passion; there is serenity. There is no death; there is the Force. The peace, the knowledge, and the serenity were gifts that came with his surrender to the Force and with his connection through the Force to all that was.
"Sustaining that clarity was always the challenge. In the isolation of a Dagobah, the Jundland Wastes, or a hermitage on a frozen shore, an experienced Jedi could preserve that inner state indefinitely. But the chaos of the real world was another matter. When ego returned, so did will. The surrender became tainted, the connection flawed. The clarity gradually slipped away under the continuous assault of elementary drives and passions. Even the greatest of the masters needed to perform the practice regularly lest they lose the discipline that made them what they were."
Compare this concept to Jacen's moment of transcendence:
"As his grandfather had done, he had broken through the apparent opposites that concealed the absolute nature of the Force, and found his way into an unseen unity that existed beyond the seeming separateness of the world. For a moment all the cosmic tumblers had clicked into place, and light and dark sides became something he could balance within himself, without having to remain on one side or the other.
"The consciousness that was Jacen Solo was strewn across the vast spectrum of life energy. He had passed beyond choice and consequence, good and evil, light and dark, life and death. All that had been required of Jacen was complete surrender -- a technique once mastered by the Jedi Order but at some point misplaced; transposed to an emphasis on individual achievement, which had opened a way to arrogance. In that the path was available to any who chose to seek and follow it, Jacen understood that the discovery was really a rediscovery."
And another discussion between Jacen and Sekot, in which I feel Sekot sums up entirely what Vergere was getting at all along:
JACEN: "And you'll exercise that power to defeat them?"
SEKOT: "If necessary -- but without contempt. If I defeat them aggressively, if I hate them for who they have become, then I will have separated myself from the Force, and permitted my ego to triumph over my desire to merge and expand my consciousness. I will have corrupted the light with my darkness, stained it forever. Self-awareness tricks us into believing that there is us, and that there is the other. But in serving the Force we recognize that we are all the same thing; that when we act in accordance with the Force we act in accordance with the wish of all life to enlarge itself, to rise out of physicality and become something greater.
"In that sense, all living beings are seed-partners, Jacen, passionate to unite with all life, and to help give birth to grand enterprises -- whether a starship, a work of art, or a deed that will echo through history as a noble action. I am no different than you in wanting to play a part in the evolution of the spirit. My consciousness yearns for this."
This perfectly encapsulates the theme of symbiosis and balance which Lucas was going for in Episode I with the midi-chlorians, the Gungans and the Naboo, and the Jedi and life and the Force.
As for Vergere's idea of control tainting one's path to greatness, control requires ego. Luke's pathway to complete surrender is incomplete because in his attempt to subvert his own darkness, he seeks to control himself from not feeling anger or hate, and allows his ego to prevent the loss of self into the vastness that is the Force. Vergere is proposing that anger is not bad in and of itself, and the darkness that the anger feeds can be eliminated through self-mastery.
If you know your inner darkness, instead of denying it as Luke did, one needs to come to know it so that it can't affect you. This is great writing, IMO, because it's taking another Jungian concept, integrating the shadow, which meshes so well with Star Wars because in addition to the Taoism that Lucas used, Star Wars is no stranger to the Jungian archetypes that Lucas used in the monomythic structure he based the series on.
So if you know yourself, when you surrender to the Force, you will be able to be subsumed by the Force completely. And now my appreciation for the New Jedi Order has increased tenfold. And I have some sense of hope in the sense that despite the ridiculous Vergere retcon, Sekot still exists with this knowledge, and hasn't been retconned into being a Sith Lord yet.