If I remember correctly the gear head and motor are held in by just a few screws. When you remove the mounting screws you want to be holding the assembly up or it will just drop, it looks like you broke everything when it slides down but everything slides back into place pretty easily when you reassemble it. The motor and gear head are attached to the swing gear, I don't know the correct name for this part, by a few screws on the back but you can get those out by feel. After the screws on the back are out then you can slide off the the motor and head. The motor is the same on all doors but the gear head is different from one side to the other. Another thing that can go wrong with the motor is the brushes that are in a holder that you can see in the pictures that I posted. There is a discussion about this in a thread titled "is my window motor dead"

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1983 300SD
200000miles