Resistors are pretty easy to replace as long as the traces have survived. I doubt that'd fix your booting/sound issues, but grab yourself a cheap desoldering tool and replace em. Honestly though, as long as they still test right with an ohm meter, just because they look cooked doesn't mean much. I've seen worse looking resistor sections that still worked just fine

Agree with wayout though, the amount of time it takes to fix boards rarely makes it justifiable if you can replace them. Anything can be 'fixed' with enough time.