Howdo I reply to summons regarding an injury in a car accident?

A lawsuit can be filed where the plaintiff resides or where the defendant resides or where the claim arose.  The statute of limitations in a personal injury case varies from state to state.  Without knowing in which state the lawsuit was filed, it would not be possible to determine whether or not the other driver had missed the statute of limitations

As for how to respond to the lawsuit with which you were served, the complaint is the lawsuit attached to the summons.  The summons states how long you have to timely respond by filing an answer to the complaint with the court.  The time starts running from the date you were served with the summons and complaint.

The answer denies the allegations in the complaint.  If you had auto insurance at the time of the accident, just forward the summons and complaint to your insurance company.  The insurance company will handle the matter for you and will provide you with an attorney at no cost to you.

If you did not have auto insurance at the time of the accident and/or cannot afford an attorney, at the law library look for answer to complaint in the index of Pleading and Practice.  This will give you the general format for an answer to a complaint.  As mentioned above, the answer denies the allegations in the complaint.  At the end of the answer is the verification which attests to the veracity of your statements in the answer.  You sign and date the verification under penalty of perjury.  File your answer to the complaint with verification and an attached proof of service with the court.  Serve a copy of the documents by mail on the opposing party or the opposing party's attorney.  The proof of service confirms the date of mailing to the opposing party.  You can either use a court form proof of service or you can write your own.  If you write your own, it just says that you are over 18 and the attached documents were sent via first class mail unless stated otherwise to _________ (name and address of opposing party or opposing party's attorney) on ________ (date).    You sign and date at the bottom.  The date you sign should be the same as the date of mailing and the same date you file your documents with the court.

If you do not timely file (before the deadline in the summons elapses) your answer to the complaint with verification  and proof of service with the court and serve it on the opposing party, a default judgment will be entered against you.  This means you have lost the case by default.  If that happens, you will need to file a motion to set aside the default.  If the court grants your motion, the case is then back on track and litigation will continue.