Read your school documents to see if you are obliged to report arrests. You probably are not. A misdemeanor conviction would not automatically prevent you from becoming a lawyer. I suggest you retain a good criminal defense lawyer who knows how to handle a dwi case and consider getting into an out patient program.
Contact a personal injury lawyer ASAP. You need to file your no-fault insurance claim form on your carrier within 30 days of the accident to get your medical bill and lost wages paid. You can seek pain and suffering damages from the woman you hit you if you show you suffered "serious injury" as that term in defined in the Insurance Law. Surgery alone is not "serious injury" but could be depending on how things turn out.
A .20 is very high.
I would be careful about broadcasting that you called in a favor... someone can get in real trouble.
You should hire a criminal defense lawyer. I can't imagine a judge would let you plead guilty to a crime without a lawyer.
Under NY law, the car that stuck you in the rear is presumed negligent and will have to give a non-negligent explanation for why the accident took place. The most often given is the car in front made a short or sudden stop. Judges usually reject that defense. Another popular (and more successful) one is that the lead car suddenly changed lanes directly in front of the car causing it to rear-end the lead car.
It is not too late to hire a private lawyer. Private lawyers such as myself carry a much smaller case load so we have more time to devote to the client and their case. I handle cases like yours all the time.