I think that valve adjustment is too critical for me to recommend that you try it on a car you care about without an experienced person to show you how to do it the first few times. Mistakes are easy to make and can be costly when valves are concerned. Loose valves won't do any harm, probably, but tight ones can cause misfire and burned valves, so loose noisy ones are safer than too-tight quiet valves.
If you really want to do this, get a manual or use online manuals for specs and procedures, here's a link for you:
Here's the one for Mitchell as well:
If you choose to get into it, you'll need the specs, a screwdriver, wrenches, feeler gauges, a new valve cover gasket, cleaner spray and probably some sealer. Remember that only a small adjustment is required, if you think you need to make a big adjustment to get the clearance right, you're probably making a mistake so recheck your procedure.
If you want to find a specialist, here's a directory link for you: