Clockman,
You can find replacement units on ebay selling anywhere from around $60 up to $120. If you are mechanical you can pull the unit out easily enough and check the bulbs first. It only takes a small screwdriver or credit card to pop the lens off, then a small torx screwdriver to remove the unit from the frame, two screws. Once that is out, the bulb turns from the top and can be easily replaced.
Good luck