If there is a balance left on the loan, you will be responsible for the amount despite the fact that your car is totaled. If you have auto insurance coverage, the insurance company will either pay to have the car repaired or will pay you the value of the car, which can sometimes be less than the amount owed. Your insurance company will then attempt to collect money from the insurance company of the person who caused the wreck. If you do not have insurance and the person who hit your car does have insurance, that person's insurance company should pay.
Your question discusses the car but not the possibility that you may have been injured. I would talk to a local attorney such as Mr. Greer prior to executing any releases so that you are protected. Many times I hvae seen a client worry about the car, sign releases for both a car and the bodily injury claim and then ask for help. Please consider this.