[sowise]

I definitely wouldn't sell the car if I was you. Check out ECU tune they can give you an upgraded performance valve body with all new solenoids for $600 if you don't want to replace the solenoid yourself. As for the C solenoid there are plenty of how to's and boards posted on this and none of this will cost $2750. Even a ECU tune rebuilt trans is $999.
I understand your frustration for having had to replace your transmission so many times but I am not sure it needed to be replaced that much. Up to you though really but I would hope you would keep your car.