Car window troubles

The loud thunk I heard when I rolled down one of the back windows in the car didn't sound good and sure enough, it wasn't good either. I can hear the window motor run, but the window doesn't do anything except make thunking noises. I'd guess that whatever mechanism makes the window go up and down has managed to disengage itself from the motor.

Managed to get the door panel off, but quickly saw that anything required to get it working again was a little past my comfort and skill level to handle. This of course means a trip into the dealer service shop for repairs.

Crap.

Hopefully it doesn't turn out to be anything horribly expensive to repair. There are already a few other routine maintenance things I need to get done to the car, and this isn't helping any.