The C64 breaking was almost certainly not your fault.. they had a bunch of commonly occurring faults, and a number of the chips, especially those which commodore fabbed themselves were notorious for giving up eventually. The PLA failing was a particularly common occurrence, but RAM and other glue logic sometimes fails too. These days there's a vibrant hobbyist community and a lot of the chips have modern replacements available. I'm still grateful for having grown up with a C64, it was a fun way to learn the ropes.