Special OEM tools and additional parts required? What, besides noise, is the effect of leaving the valves as-is? Increased wear?

Since I've had the truck at 135K (it's now at 160K) its had some valve noise. I listened through a steel pipe and its coming mostly from the valve covers (and exhaust manifolds) and not the timing cover.

CHRIS
98 Amigo, 92 Pup

need a pickup 1st gen fuel level sender