I think that some of this CS-80 problems can be solved with a refurbishment (old CMOS, old el-cap), but i know that probably (and unfortunately) not all the problems will be solved in this way, but in the meantime i know that i have a good starting point (i hope I explained myself).
I totally agree with you on "don't change two things at the same time", it creates even more mess!
Best
Mark