If it's still under warranty, just give dell a call. Don't have to mention anything about you updating the firmware, just that it seemed to have stopped working.
If not, you should be able to find DVD-ROM replacements on eBay.
Also, you might be able to find someone in your area that has a Dell 8xxx series. They might be able to better help you as those lappies can take both units with a little modification. Taken apart my 8000 here before so it's not hard at all.