No no no. Tell them they can take the car back because the fix isn't going to be exactly what you thought it would be. You don't want this car. What is the period of time you have to return the car for a full refund. I would complain to everyone until you get a new car. Don't let them make you take this car and don't get so attached to it that you can't let it go. If it is such an easy fix they shouldn't have a problem taking it back and dealing with it themselves.