Head gaskets are fairly simple to replace, they just take a fair amount of time, Most shops will charge alot to do it just because of the time involved. Crazy because all need to buy is the gasket and silicone, and need a good torque wrench. You basically have to take off the entire top end of the engine.
If your not in a jam, and have extra time I would definately do it. I think I have to replace one on my mitsubishi.