wiper on back window

Can anyone tell me how to change the wiper motor for the back window on my 1999 jimmy. the wiper just comes up about 2" and stops. Any help would be very much appreciated.
Bush

2 or 4 dr? If its a 2dr, put the tailgate down and remove the plastic and metal panel to access the motor. If its a 4dr, the entire tailgate panel is one piece that comes off to access the motor.