This might be a little late, but...
You can usually just replace the motor, but if this is the first time you might want to pick up the whole motor and regulator kit. Also, since you are taking it apart, check out
AutoTrix Passenger Fix Kit - This wires directly to your battery so the passenger motor is getting a full 12 volts instead of taking power off the driver motor. Makes it faster and makes the motor last longer.
__________________
461ci, Edelbrock 72cc heads, KB 15cc dished pistons, comp xe274, PRW 1.5 roller rockers, Performer RPM intake, Holley 80508 750cfm, RARE oversized manifolds, Pypes X-pipe Exhaust