Put a towel on a solid table and turn the car upside down so the head is resting on the table. Use a #2 phillips driver with a good tip. Hold the screwdriver with one hand and the car with another, put your chest on top of the hand holding the screwdriver and use as much of your body weight as possible while turning. If this doesn't work, or the screws are already stripped, you can use a dremel to cut a slot in the screw head. Then you can use a flat head driver. You car also drill out the head using a 1/8 inch drill bit and your favorite drill.
I wouldn't heat the car up on the stove. You run the risk of melting the plastic and getting some burns from overheating the chassis.