Prying on the mating surface of the cylinder head is a very bad idea. If memory serves, you need to remove the cam to access all the head bolts. Make sure you have removed all of them. Also, be sure to remove the support bracket under the intake manifold. Lastly, in my experience, head gasket failures on that engine are very rare because it uses an MLS (Multi layered steel) gasket. I would make double sure you actually have a head gasket issue before replacing it. Air in the cooling system is the #1 cause of overheat on those engines from what I’ve seen. More info here.