I think i blew my head gasket, how hard is it to fix

You're looking at removing the valve covers, intake, nearby components that are obstructive to the task, and labeling and numbering rods for the order they go back in.

all depends on how much effort you want to put into a 91 GM, really. How do you think you blew it, what happened to it that makes you think that happened. How long have you had the vehicle??