Unfortunately, I don't have the answers to your questions. Though I'm an engineer, I'm of the wrong persuasion (structural) when it comes to serious soldering on such a unit. I still have the original schematics that came with it. If you're interested and think that they'd help you out, I can scan them and send the PDF's to you. I think that these things have enough of a cult following that even a parts machine may be pretty spend and/or hard to find. From what I gather, will regards to replacement capacitors/transistors, I think you can still get everything you need aftermarket with the exception of the four big (oval) power supply capacitors. Regarding replacement knobs and switches (if needed), that may be quite a bit more difficult to find.