I did the research on the Envoy door switch. The first thing I noticed was the number of plugs and wires going to the switch assembly (4) one with 12 small wires. As it turns out, the switch IS part of the door module and has to be "flashed' (reprogrammed) for the CAN (Controller Area Network) to recognize the new module. I found a company called "Auto Flashers" here in Houston who came out to my hobby shop and performed the flashing. The dealer wanted $148 plus tax (and other fees) to flash the door module. Auto Flashers charged me $115 to flash the door module and flash the PCM and BCM with all the latest software updates. Several to prevent false codes. As I said, they came on-site to do the work.
Flashing is not something that an individual can afford to do. You have to have a laptop with a serial port (business or professional), and interface unit with software/drivers, and access to the updates witch requires a subscription to your carmaker. Updates are downloaded to your PC and then transferred to the modules through the interface. The process is fairly quick, but the equipment and information is expensive.