...a leaking head gasket will usually make the bike seize, which is what may have happened in your case (piston gets too hot and seizes).
There is too much to list but all very basic and easy to do with comon hand tools, AND a shop manual...there is going to be no other choice but to find/borrow a manual or take it to someone who is already savvy. You must figure out if the rings are stuck in their landings/seized, as well as why the head gasket was leaking in the first place. Be careful that you do not put good $$$ in a hole, as anything older than 10yrs is going to often be much more $$$ in OEM parts than a modern bike. My advice is to get it running on the cheap, ride it to make it last, save your $$$ and then add it to what you can get for this bike and buy you a much fresher bike for ~$1500. The absolute best Manual/educator I can recc is Eric Gorr; visit his site and buy his $20 manual---the only other person I "worship" is SuperHunky (he has some great money-saving articles on his site, offroad.net/dirtbike)...stick with it...! <g>