Landrover 90 Defender 1990- Rear Wiper Motor?

Does any one know how to repair a Landrover 90 Defender - Rear Wiper Motor? it started making a right noise, then blew the fuse. I have looked at it and one the bushes is really warn. Is it possible to carry out any checks electrical or otherwise when the wiper motor is off the vehicle.

Or do you know where I can purchase one on the cheap :-)) Due for it's MOT 01-06-10.