You will not be immune to a suit because anyone can sue you if they so choose. If she does indeed file a suit against you, then at that time you will need an attorney to file an answer and handle the litigation.
You should seek a litigation attorney who deals with issues of defamation, libel. etc. Most general litigation attorneys will probably be able to help you. Feel free to contact my firm for a consultation if you would like.
You can sue someone for unjust enrichment and account stated if there us a contract involved - I don't know the details of your contract/lack of contract though. The bottom line here is that you need to respond to the complaint by filing and serving an Answer. Otherwise they will get a default. I would suggest hiring an attorney to do it. Then they can also settle the balance, unless of course you do not legitimately owe them anything. I work on many of these type of cases. Feel free to...
I would suggest - and this is not a purely legal position but practical as well - that you do not put the car in someone else's name. If there is any issue down the line between you and your co-signer then it could cause serious issues if you are paying for a car that is not owned or registered by you. Why don't you just have to co-signer co-sign on the loan itself, but title and register the car in your name?
Was there a will? Was there money/value in the estate? Did you have a pre-nup? Generally you can not be cut out of an estate as a spouse, so you may have some recourse here. Answering some of these questions would be helpful.
You or your son should get a copy of the will and maybe go through the courts to get it probated if it's not already. I suggest having an attorney help you with this. As for the abandonment of property, have an attorney look at the documents - otherwise it's too speculative.
You should take a look at the contract you signed when you purchased/traded in. Normally the dealership would pay off your old car as a trade in. Did they take the car? Did they then re-sell it? If so and if they did not pay off the vehicle in violation of the contract, you may have cause for a lawsuit against the dealership. The bank financing the original car will not help you - they just want the payments made. The fact that they may have been closed since Sandy does not necessarily mean...