Amp Upgrade - Capacitors, Resistors or both?

I own a old (circa 1980s) Counterpoint SA 12 and love its sound. On various threads here, I learn that to get really good sound from an old amp, internal parts need to be replaced.

First, is this true? I've nothing to compare against, so don't know if I'm missing anything. If I need to, should I think about having the capacitors replaced, or the resistors, or do I need both?

Not sure what this would cost, but  knowing what I need to do would be a starting point. Ideas, anyone?

gasbose