Take a look at my posting on removing a broken bolt. As the clencher says it is easy! Get your hands dirty and give it a shot. If you have a bit of it sticking above the head welding a nut on top is a great idea. If it broke off because it was cross thread, just drill it out and install a King Cert. Wouldn't replacing the head cost money?
I had a bolt break on me when I replaced my muffler and I couldn't get a bit to stay on it to use the extractor, kept wanting to creep to the edge, not to mention it was under the car.