/diy/ - Do It Yourself

Hey lads I just got a hold of a vintage nad model 90 amp and I was looking for some servicing tips. The only service manual I could find is some sort of fucking bootleg copy scanned with an early 90s cheapo scanner and its barely readable.
I know that the the thing needs a recap starting with the filters which are completely gone as the heavy humming from the outputs suggest. What else should I preemptively replace ? I know that carbon resistors go bad so Imma do away with those too but I'm really worried I will bork this by cheaping out on a component that's going to take the output stage with it. I head that those ball shaped semiconductors may go open too but I don't know if it applies to this era of electronics. Also what brands/series of caps do you recommend for amps and filters ?