Yes, you didn't state what you want to achieve with a real classic Amiga. Are you a gamer, collector, retro-computing geek? Do you have delusions (as some of us do) of trying to do as much as possible with an Amiga?
You may be able to replace the yellowed keys from a defunct keyboard. Some have acheived admirable results with paint (others beaten their machines with an ugly paint stick, grin). There may be cases and keys available from ppl who have towered their systems.
I agree with the above, your symptoms sound as if you have developed an intermiiitttant connection. I would try carefully cleaning all contacts with isopropyl or maybe an eraser and giving attention to the way mating connections seat.
I'm not aware of anyone successfully using a 3.1 rom image file in a system like yours, but maybe they have. Amigakit probably sells 3.1 roms if you've been put off e-Bay.
Getting the real hardware may be more important than cosmetics. Welcome back to classic Amigas!
