I would be very surprised if you have a broken bolt in your mount. Usually the rubber "insert" in the motor mount breaks down and separates allowing the engine/trans to drop. I was able to buy just the insert for my 98 SE from NAPA (about $30) and replace just the insert. Much cheaper than replacing the entire mount. If that works for your car you will have to pull the mount (Only pull the half that holds the insert), bend the tabs that hold the insert in place, push the old insert out, press the new insert into the mount and bend the tabs on the new insert to hold it in place. Then reinstall the mount.
