Honestly, if it's bad and you need the block trued, it's expensive. If it's minor, and you think you can get away with just replacing the gasket... You could get away with about 300$ in parts. Head gaskets are serious work. If you are confident, and are good following directions, it is doable, but there are a lot of things you could screw up. At the end of the day, it comes down to your ability level, if you're having a shop do it. Get a couple grand set aside.
2003 Mach 1