I would consider a $700 thermostat and coolant flush high. If the thermostat is under the car like my daughters 2017 Fusion Hybrid, this is not a difficult fix. If it's buried in the engine then it's probably better to let the shop handle it. I'm getting ready to do a flush and fill on the Fusion and appears to be easy access to the petcock on the radiator and thermostat for draining the coolant. The most difficult pat of this job may be purging
the air from the system when finished. Check out the YouTube videos to see if you can handle it yourself.
