Fix or sell?

I've a 2016 ST3 which has just hit 100k miles. Was in a minor collision 2 weeks ago whereby someone reversed into the side of me (low speed, but need 2 new doors). Last week, engine has overheated when driving (not likely related to the crash). mechanic thought it was the thermostat but not thinks it's the head gasket and seemingly doesn't want to take on the work for this. I can't get my car to the body garage to get the new doors on.

is it worthwhile spending the money to fix the engine issue or sell at a loss and move on?