96 cierra power issues

This is going to be a long story. I have a 96 olds cierra. The brakes have been acting up for a long time due to a short in one of the harnesses. This just causes the abs to not work when it rains or randomly. Not the main issue. This has been happening for years. The new problem that might be related or not is that the battery keeps dying. I noticed a while ago that when I pressed the door locks the dome lights dimmed dramaticly and then the door locks stopped working for a while. They started working again and I continued to drive the car. I bought a new saturn and am loving that so I don't drive the olds that much anymore. I am selling it to a friend so I was checking it out and now the battery has stated dying again and when I shut off the car the ignition seems to have an issue. When you shut the car off it automatically unlocks the doors and turns on the dome lights. Now it sometimes gets clitchy and keeps trying to unlock the doors. Are all these problems not related or could it all be a wiring problem. Also any ideas how to fix any of the problems would be great.

Thanks in advance

Jonathan Bowen