Changing the TCC is a piece of cake to do....
But getting at is is a whole other story. The transmission has to come out in order to have room to pull the side pan. After that pan is off, the TCC is held on by one bolt and a harness. One would also need to replace the side pan gasket and side pan gasket around the cv axle. These can be had at most transmission shops.
If you're actually pulling a code 39, it could just be a short in the wires somewhere. Check the harness at the transmission for corrosion. Otherwise, dump in some seafoam trans fix and hope for the best....
RIPBC... Off to bigger and better things