Google it, and with enough searching, you'll find a mod available for the Air's superdrive to make it work with any Mac. It will cost you about $10 to mod the drive...
I'd say also check how much Apple would charge you to fix the drive outside of warranty...I don't think it would be more than $150. I know that's a lot for a DVD burner, but you're essentially going to end up paying $120 or so for the Superdrive + mod and you'll waste a USB port and it wont look as pleasant as having one built into your machine....