Time for a better truck shop.
I can even make Dodge trannys decent with a good rebuild. A 97 F150 should be childs play, no way they eat 10 transmissions in a life time even with crazy towing and offroading.
Fluid blow out at flywheel? Front seal or pump failure? Bad torque convertor? O-ring. Could be many things. But sounds like an easy fix, unless it's been slipping and cooked again.