Sorry you are going through this dirdie but I agree w/Lynne+Co in this case.
IMO, It will be difficult for you to prove negligence on the part of the vet at this time and possibly even in the future.
You'll need another vet to say (in a legal way) that the first vet made errors. Given that saying this (or even writing it) puts the time of this new vet in jeopardy, (court appearances, potential paperwork) most vets will likely not want to do this. If you pay them for their time as an expert witness or to write an affidavit, or they have a huge heart and do truly feel the first vet was negligent...maybe they'll do it. Most likely they will want to be paid though as their time is now implicated.
If you went head to head with this first vet in a legal way, after gathering your own evidence, you should expect that the vet would have a reasonably good chance to explain why what happened happened so that he wasn't at fault. You'll really need somebody with you (probably a vet) for your best chance at recovering any expenses.
No matter what though - I wholeheartedly agree that a new (recommended from somebody you trust) vet is in order.