MCU (Media Control Unit) is a computer system that controls the infotainment and HVAC system of your Tesla Model S. If the MCU is indeed broken, it will need to be repaired or replaced by an authorized Tesla service center. The cost of the repair will depend on the extent of the damage and whether the unit needs to be repaired or replaced. It's best to contact Tesla customer support or an authorized Tesla service center to get an estimate of the cost of the repair.
Keep in mind that Tesla Model S is an older model, and repair cost may be high, in some cases it could be more cost-effective to buy a new car.