850 CSi sideview mirrors

My sideview mirrors are experiencing potentiometer problems. They no longer know where they are. My master tech says that the motors are sealed and cannot be repaired. If I want my passenger mirror to gently look down when a back up and return to the original setting when I begin to move forward I need to replace the mirrors at a cost of greater than $500 a piece.

Does anyone have experience in opening the mirror motor and cleaning the contacts?

Thanks.

SpdyOB 1994 850CSi