Thanks for the reply Ifly. I'm not sure what caused the cracking but it may have been the result of a tipover and the motor trying to turn while the prop was stuck in the ground. Others have reported the same problem for no apparent reason. I superglued the cracks but a chunk of plastic broke loose and fell out from around the bottom near the screws so I don't want to risk it anymore. I ordered a shell on eBay and it's all disassembled now, that was the easy part.
Thanks again for the advice, I'll post my re-assembly results in a week or so.
Well I got the battery door out of the old shell, it's the only thing I could salvage from it. Transferred all the components to a new shell, it took about three hours. Flew it today and it's as good as new.