Blazer

This is a job you should not do unless you have a fair amount of past mechanical experience, also you should get a manual and read up on the procedure and check that you have all the required tooling, start here.

Mark (mhpautos)

If you never done such a thing I suggest you have an experience peron beside you to guide thru there's other process you need to do other than replacing the gasket such as alignment/valve and ignition timing before and after you replace the gasket-