My dryer will not start and the manual says it may be the thermal limiter. Is this costly to fix?

The thermal limiter is like a fuse that can not be re-set. They are fairly inexpensive, $25, but you will need to open the cabinet to get at it. Don't remove any parts until you have the replacement part in hand so you'll know what it looks like. One or two screws and unplug two wires and you're fine.