Gasket: I understand Felpro now makes the gasket and it won't rot like the older ones. Clean the bolts and load them down with the lock-tite that looks like wood putty. Definitely go back to good old Prestone and rock on. I gave you the same info as rhandwor but just confirming it for you.
There is a TSB for the gasket replacement with a parts list so use the forum search engine and you'll find it. Or, swing on by your ringy-dingy-doo-dah-day Chevy dealer and ask them for a copy of the TSB.