Weird. I also snapped a bolt when I had to do a valve cover gasket and I was using a torque wrench. Mine was on the side where it the bolt comes out the other side so i was able to back it out with a pair of pliers very easily.
These bolts go in and out very easily, you shouldnt' have too much of a problem getting that one out. Ford sells new bolts they are pretty cheap.
2. Get a new gasket.
3. Pull the washer through the gasket. This keeps the gasket in place as you flip the valve cover on to the head.
