I was thinking these were valve-in-head (not sure if that's the term used), but you can re-use the cylinder head bolts after removal. Before you get to the task of removing the cylinder head, just follow Jerry's advice & see if any of the engine's ailments work themselves out.
There's also a few
tech tips on these procedures, but here's the shop manual links:
Point gap in the manual. Valve clearance procedure . Yes, the valves need to be adjusted while warm, but you need a baseline starting point since the engine has set idle for a while.
Valve timing. What color smoke is it?
Brad