You should use avvo find a lawyer to find an attorney in the area where the case was filed. Lawyer there will know the answers as to the statute of limitations, venue, jurisdiction, and service, as well as whether your failure to file transfer papers with the dmv before the accident makes you legally liable.
The question is convoluted, and without all the missing relevant facts, tough to answer. Best speak with one of the local Avvo lawyers on the phone who can separate the wheat from all this chaff.
Any defects in the case brought by the Plaintiffs, and any available tot he defendants are best addressed through hiring experienced counsel if you did not have insurance at the time of the incident, and giving this to your insurance carrier immediately if you did have insurance.
. Time's is rapidly closing to successfully do anything. If you do not already have counsel, dix that problem this morning.
As the other attorneys have stated, you really need an attorney for this. Hopefully an attorney can dispense with it as to the sellers quickly and inexpensively. If you do this wrong from the start, it is going to cost you more in the long run. First, ask this question in Georgia (or call a couple of attorneys directly). I doubt the sellers are liable but in CA there is a release of liability form that must be completed and you will have to find out if the same exists in GA. I doubt service was proper, especially if each defendant was not personally served. Venue and jurisdiction are likely proper if that is where the accident and sale took place. For you to be compelled to answer however, you need to be served here in CA.