Well, looks like I've been struck by the window bug. My driver's side rear window wouldn't move up or down this morning, but I could hear the motor churning. After some tugging, it has slid to the down position and won't budge past halfway up. Motor still "moves" when the button is pushed. What is the procudure to get it back on track, I believe this is a common failure, what parts issues are there, and is this a DIY type deal? I'm willing to spend a day on it if I have to, but I've never opened up the back panel before. Thanks for any and all suggestions...

PS it's a 94 S500 coupe, so no rear side airbags....