The module is screwed to the inside of the door. You will have to remove the door panel. It cost me $100 for the used part . The dealer wanted twice as much & also said the module had to be reprogrammed for the options in the car. The used unit was matched from a wrecked vette with the same configuration so no programming was necessary. You have to have a little mechanical sense to get the door panel off but the rest is just a plug in.
Before you spend money on a door module. Inspect the connectors that join the door harness to the body harness (should be numbered connector 200 in your service manual), they can be reached by pulling off the passenger door sill and removing a small black plastic cover just below the dash. I have had several instances of these connectors having loose terminals and causing the exact problems you describe. A quick test is to wiggle the black rubber boot that runs from the door jamb to the body, while trying to operate the window. It should start working if only for a few seconds.