I know James did a head off job on the veccy and included plenty of pictures and the like. Have a trawl.
It's not a necessity to disturb the valves if you want to do a quick job. However, If it were me and the engine was on 100,000+ I would probably take each valve out and lap it back into the seat to ensure a good seal, and fit a new stem seal (included in a head gasket set 99% of the time). Just need a valve spring compressor (with a long reach), some valve grinding paste and a stick with a sucker on the end. I have these if you want to borrow them.
I might be inclined to clean out the hydraulic followers as they'll be coming out... See Mark's HOWTO.
The head probably won't need a skim, as you've caught it in time. Make sure the mating faces of head and block are spotless before assembly, though. Not sure what the best policy is on re-use of head bolts on this engine. Often a head gasket set will include new bolts anyway and they are normally streatch bolts these days so new bolts is a safer option.
In light of common problems, it might be worth checking the exhaust manifold for cracks and fitting a new gasket and studs, with a little copperslip, whilst the head's off.
But before that, make sure it really is the head gasket. If it runs on all 4, a compression test probably won't be conclusive. Get a garage to check for exhaust gases in the expansion tank.
Kevin