Ouch! Sorry to hear that! Personally, I'd insist on new OEM parts for replacement, since it's obviously their fault. I'm also not sure I'd trust them to fix it in-house unless I knew them well. They'd be motivated to fix it as cheaply as possible since it's coming out of their own pockets. Take it someplace reputable and send them the bill. For parts I'd try the local dealer and here:

www.bmaparts.com
www.carpartswholesale.com (not OEM)