I don't see any pictures posted in this thread, but if you want to email/pm them to me I can take a look at. I do all the welding for our machine job shop (including aluminum TIG welding), and unless the pan is severly mangled, I would anticipate that it should be readily welded - would need to be thoroughly cleaned prior to welding. If the damage is in/around any sealing surfaces, it may require some machining after welding.
Regards,
Andy
adunnell@netzero.com