George, if it is just siezed or snapped off in the housing, it can be repaired. Once you have the cover off get us some pictures of it.
If there is enough of the bolt sticking out, I have had great luck welding a nut on the broken bolt, and getting them out.
If there is enough of the bolt sticking out, I have had great luck welding a nut on the broken bolt, and getting them out.