Realistically, you are looking at 400 to 600 dollars to fix this. That is to do a torque converter, install the valve, and a new filter and fluid, of coarse. I think this is a fairly cheap price.
Personally, once the tranny is out of the vehicle, to replace the tc that has been forced to slip for so long; I would at least inspect the rest of the unit. There are too many parts that are known to fail to not do this.
I am in Massachusetts and if you where close enough I would be able to help you out on keeping your costs down.
Hope it all works out for you