I have a recently purchased second hand sander that I wish to do some modifications to. Tonight I notice that the bearings in the tracking wheel and the top wheel seem to be spinning "noisier" than usual. Turning the wheels by hand seems to suggest that I should replace the wheel bearings before investing a lot of time into the modifications. Has anyone done this before ? I removed a snap ring in one of the wheels, but the wheel and bearing were not going to come off easy, so I thought that I would ask the question before I possibly do some damage.