Well, it depends on the nature of the trial. Since it's your fault, and you admit that, then it's just whether or not their claim is being paid for by your insurance company. That should be the end of it. I'd recommend talking to your lawyer to find out the exact details of the case. Frankly, this sounds like they're suing you being you/your insurance is not paying, or not paying sufficiently, for the damage on their vehicle or hospital bills.
If it's something like emotional or physical trauma, and unless you really slammed into them, then it's likely just the American dream a frivolous lawsuit you've been slapped with. Your best bet is to talk to your lawyer, get a copy of your insurance contract, and comb through as much of that with him/her as you can regarding the specifics of the case, and how it is covered in your policy, and how extensive the damage.
On top of that, ask the prosecuting party for a copy of the quote for their car repairs, reference it with a quote for the same services from another mechanic. Basically, set up as much in your defense as you can. If this lawsuit smells fishy, which it very much does from here considering it's for minor car repairs on a 2-year-old accident, then see if you can cover your legal butt for any fault you may have had. The only way this lawsuit could but mustard is if they had driven/restored a very expensive antique vehicle, or made extensive modifications to one to merit a price larger than your insurance policy would cover.
So yeah, in this order:
1. Contact your lawyer. Go over the fine points of the suit. Figure out the who, the what, and the why of this lawsuit. Once you do that, research what you can from this end.
2. From that, have your lawyer call theirs, and really get the skinny on what they're looking for. Figure out why this suit is showing up now, and what had happened that would call for it.
3. Consult with your lawyer about reasons this suit could be thrown out, or settled for a reasonable price. This one's entirely up to you, but if you're feeling the short end of the stick in this, you don't have to sit down while it happens, it's your right to contest it.
4. Play it smart. Threatening prosecution, trying underhanded tactics to get it thrown out, or any other unsavory business could put you in a nasty position. Ask your lawyer what his/her advice is, ask why this is his/her advice, and what the other alternatives are. Talk to your insurance to see if they'll opt for covering the settlement, since this should fall under accident coverage. Don't be afraid to consult your lawyer about everything. It's their job, so they generally have a good idea of what the best courses of action are.
5. Good luck, play it smart, and walk the straight and narrow.
