sure it's been covered before, but here goes:
1. fabricate a chain tensioner out of wood (chiltons has a good picture) or buy one from MSA
2. hammer the CT down between the chain
3. make sure that tensioner is tight!
4. see #3 (i cannot stress the importance of this!)
5. unbolt the cam gear
6. using a hammer and a small piece of 2x4, knock that cam gear off the cam
7. get the chain off the gear (make note of the dots)
8. remove head, careful not to knock the CT loose
9. clean surfaces and put new gasket
10. reassemble
EDIT - pick up a chilton's or an FSM. pretty much mandatory if you're pulling your engine apart.
search the forums for more in depth 411