pretty easy to adjust valves. Pretty similar to the F-Series of engines.
run the engine until it warms up.
pull the valve cover
disconnect the ignition coil.
Pull your spark plugs.
turn the engine to tdc by the crank(17or 19mm) with the transmission in neutral or put the transmission in gear(standard transmission only) and use the bump method-rocking the truck back and forth on level ground to slowly turn the engine.
you'll need a flathead screwdriver, i think a 14mm box end wrench, and some feeler gauges.
look up the specified lash on particular valves at specific in the fsm. Some people adjust them tighter than spec for quieter operation, but there is some argument that factory spec increases longevity of the engine. It should sound like a sewing machine. when you're done
Think the fsm goes through the process fairly well.
you set specific valves at tdc, then I believe others after one revolution of the crank.
Needs to still be warm when you're fiddling with the valves.
If you haven't used feeler gauges before, you insert the metal end inbetween the arm and the valve stem end. if should have slight drag and resistance, but not a grinding feeling. You break the locking nut w/ the 14mm wrench and turn the adjuster bolt with the flathead. when you're happy w/ the valve lash, hold the adjuster bolt in place and snug the nut down. You don't need to crank on it, just snug.
I like to brake all the nuts loose first, then insert the feeler gauge inbetween the arm and the valve stem until it is tight, then back off a little bit and check the drag. Check them all a couple times.
IF you haven't changed the valve cover gasket in a while, now would be a good time to do so.
there should be a few good how-to writeups floating around.