changing a thermostat on 2006 Ford Fusion

My local Pep Boys is giving me an estimate of approx $330 to change a thermostat. This includes a flush & fill which is needed as well. Is it mandatory that a flush & fill be done?

Asked by for the 2006 Ford Fusion
So much coolant will come out during the repair that you'll need to add more. They could just add more coolant if it's cheaper than "flush and fill" service.