The contacts were meant to be cleaned. It was an easy job as I recall. I believe I did it twice, once when I re-soldered a connection. I've never replaced a Commodore/IBM/Lexmark keyboard.
It takes a keycap remover (mine are home made), compressed air, isoPrOH, an emery board, and a pencil eraser for 99% of them. I've re-soldered a few wires and a blown LED, but the layout is not cramped.
I've done PET, C64, A1000, A2000 and A4000 keyboards with success each time.
