Starting with the door panel off and all parts removed from the door, I put my vent subassembly into position first, but left it loose. Then I put in the crank mechanism, loosely. Finally I lowered in the side glass and fit the pieces together.
By guide tracks are you talking the felt channel that is like an upside down L? If so, I put this in last. I dropped the side glass 90% of the way down, the pushed/coerced/crammed the channel from the outside into the small space between the glass and the frame adjacent to the door latch. It is hard to get it started, but once started, you can then push it down until the upper (horizontal) section mates with the frame. I had to use more elbow grease than I expected.
Like Bill said: not easy, but with patience it's do-able.
Bill
