The best is the actual Factory Service manual for the Riviera/Reatta, preferably the final edition. I believe it was published by Helm and can sometimes be found on eBay.
It probably could be done that way. I bought an emulator from Moates that plugs into my ECM prom through the zif socket in my modified prom. I did actually drive the car running on the laptop but I just have not dedicated the time to it. I have looked at various holders for a laptop in the car but the Reatta is not very friendly to that. A helper in the passengers seat would work far better?
Yeah, someone broke it and did a down and dirty repair. The good news is it appears that you might could change just that part of the latch by removing one screw. You might have to buy the whole door to get the part. Check with Jim Finn reattas60@gmail.com