How do you install a backrest motor?

[otto huber]

The car is a '81 300SD

A while back I replaced the seat switch for my passenger seat since the back rest button was busted and the backrest wouldn't move. After replacement, I still have no backrest movement. There is no motor noise, so I assume the motor is shot. I sprayed all contacts with Deoxit. I took a look under the seat and it looks like three motors are encased in a black shell. When I go to the junkyard, what exactly is it that I need to pull? The part # I saw on the shell was 126 820 1042.

Thanks