One thing you might check before you go tearing into anything or spending a bunch of money is the rear window wiper. If you removed it recently or moved it by hand, and it isn't set in it's "resting" position, the window switch will think it is in an active position and will not function. So try moving it by hand up and down a couple degrees while turning your key in the tailgate and see if that works, if not, then I would check fuses and motor. Good luck
-Brian