If they broke it, they should fix it. End of story. If they refuse, tell them that you will be telling everyone you know to keep away from their shop (esp. with the fender damage).
If you're feeling brave, you can trace the wires and check them against the FSM (you want section EL):
http://www.nicoclub.com/FSM/240sx/91-94/
Did they cut any wires? What does the headlight open/close button do (the one on the dash by your left hand)?
See also:
zer...25033. On my car it would blink like that, but only sometimes. I would also only have one lamp light up at a time. I took apart this switch, cleaned and tweaked it as described, and added some dielectric grease (spark plug boot grease). Never had problems again. Beware though, that switch is not fun to take apart/put back together.