What are my rights concerning a claim from an insurance provider from an auto accident(noninjury) which may be inflated?

I was involved in an auto accident(noninjury) on a bad wheather day. The road was slick and the other driver stopped suddenly and I rear-ended him. My insurance had lapsed and had been reinstated later that day. Unfortunately, I wasn't covered for the accident and the other driver has had his truck already repaired. His insurance provider sent a bill and I put it off so now there are attorney on his side involved. I can accept that I may be required to pay for some damage but I think that this guy is inflating the bill. I make meager wages and I have a family (thankfully wasn't injured in the accident) to provide for so I cannot afford an attorney. What are my legal self remedies.