You should absolutely get a lawyer to help you. There are first offenders programs that may be available to you to keep your record clean. An attorney will be in a better position to negotiate a favorable disposition with the District Attorney.
It really depends on the position of the District Attorney, and whether you actually have legal grounds for the MAR. One reason would be that you did not have an attorney and did not sign a waiver of counsel. Some DA's will consent to setting aside a plea of this type, while others never do. It would benefit you to hire an experienced lawyer that might be able to get you in front of a good DA and good judge.
The DMV restoration fee is separate from the court fines and FTA fee. You should bring proof that you sold the car when you go to the courthouse. If you are able to speak to an ADA, they might dismiss it since the car was sold. If not, I would hire a lawyer to try to get it dismissed for you. The attorney's fee should be less than the fine, costs and FTA fee. Then all you would have to pay is the DMV reinstatement fee.
The state where the accident occurred will have a significant impact on whether an attorney will take your case. North Carolina is one of only a few states in which contributory negligence is a complete bar to recovery. That means that even if you were only partially at fault, you cannot recover. If the accident occurred in another state, you may have a better chance of recovery.
Consult an attorney in the state where the accident occurred immediately.
Mr. Percise is absolutely correct. Improper equipment should be the first option, followed by 9-over.
There are many courts that will chastise a parent that shows up in place of a son or daughter. I would highly recommend hiring an attorney if the driver is unavailable. It is usually not a good idea to try to call before the court date. There are simply too many cases in the system for the ADA's to deal with them in that manner.