Doesn't work that way.
OP, when they give you their value, you don't have to accept it right away. Your best thing to do right now is to shop for a similar mileage, same year GP and get an idea of what it would cost for you to replace the car. Go from there with negotiations. With you being a new customer, more than likely they'll try to lowball you. When they give you their offer, also ask them to check on how much it would be to buy it back from them. If you go with that they just deduct that from your payout. Don't get your hopes up though. My insurance still wanted over 3,000 for mine and that thing had a effed up motor, tranny, and radiator.