Proto-
Tip #1- get at least a Chilton book, it tells you how to change the fuel filter and adjust valves. If you want to go any deeper, you need a service manual.
#2. You say it loses power when it gets warm? Could be fuel return lines or air getting in somehow. How bad is it rattling, esp under load? MPGs down? (besides the customary 10% for winter). Ok- though not great- on bottom, but gets doggy at higher loads/ RPM?
Valve lash- . 010" intake; . 020" exhaust.
Find TDC, either with the timing pin, or the valve overlap method, which is still above my head... . Using timing pin, (under the pump on the back of the gear housing, above and to the insde of the PS pump, real PITA to get to), make sure it clicks into place. It will go in quite a bit before it rides against the cam gear. If your fingers are small enough, you can take the pin out, and stick your finger in the hole (no comment from the peanut gallery, CB or EC Jay

), and feel for the notch in the back of the cam gear as you turn the engine.
ONce you have accomplished that half hour task, you are ready to adjust the valves. Remove the valve covers, and adjust the Intake and Exhaust on #1, then alternate I, E, I, E on cylinders #2, 3, 4, 5. In other words, Intake on #1, 2, and 4; exh on #1, 3, 5. Mark your H- balancer, turn the engine crank 360 deg. Start at #6, doing intake and exh, and alternate as you come forward one vlave per cylinder, doing I, E, I, E, on #5, 4, 3, 2. Clear as mud, huh? Intake valves are the frontmost valves per cylinder; exhasut are the rear, and slightly outboard ones. If you have any oil seepage from the gaskets, I'd recommend replacing them, but then I hate any and all oil leaks. Sometimes you can reuse the gaskets, but they usually start to leak after the second reuse.
Good luck.
Daniel