I received a civil summons--HELP!

My husband and I had an auto reposessed in 2006 and it was then sold for less that was owed on the acct. The loan was then sold to Midland Cunding LLC (which I have heard alot of bad things about) and they are sueing us for the remaining balance of $18000.00. We received a civil summons and was told by the Sheriff that we have to answer the complaint. However, we have no idea how to go about this. We did not receive any sort of answer form with the summons. We were told we have 30 days to answer. Can anyone help with this? Any advice would be greatly appreciated!! Thanks

First of all, the "Sheriff" was a process server---this is not a criminal complaint and it should have nothing to do with warrants or jail, etc. Now, when the car was sold, how much was it sold for? $18,000 is the original amount, or the deficiency judgment? What does the complaint say exactly? Also, I am not sure that the loan was sold if the car was repossessed. If the car was taken back, that means the original creditor has the collateral--and cannot sell the loan and keep the collateral. If they did, it would mean someone else is attempting to collect payment for collateral a third party has in their possession.

Apparently they sold the outstanding balance due ---i.e. the difference between the loan amount and the amount for which the vehicle was sold. Are the attempting to collect the full amount of the vehicle or just the amount of the deficiency judgment amount? OR was the loan sold BEFORE the car was repossessed?