Once you get the dash out of the way you'll be in just about the best position possible to clean up your wiring underneath it. Pull the trim panels underneath it, the right and left kick panels, the console, the glove compartment, remove the nuts to lower the steering column, and it's all there in front of you. Anything in the wiring which looks wrong probably is.
When I started diagnosing and correcting the problems in my '88 it was a disaster due to PO "modifications" and "repairs". I'm talking vacuum lines tied into coolant lines, hot wires connected to nothing, others tied into multiple other circuits and held together with just electrical tape and gravity. The best advice I can give is to just take on one specific problem at a time and work through it before moving on to the next one. Once you know you've got that one correct you can eliminate it as a potential issue when resolving other problems.
