Don't understand "Truck has about 26 miles . " Do you mean 26 miles since trans rebuild or 26k miles on truck?
When I had my DTT built I think the billet input was around $700 for the part and no extra to install while the trans was being built. Not sure how much for the trans R & R then bench labor? All totaled: part, R & R labor and bench work I'd have to guess and say about 1400 - 1600.
The nature of your thread, noticing the first reply "If you are in the Colorado area either myself or LaserBob can assist you with a DTT spec transmission. ", is a good reason why it's better to put your town and state next to your "screen name". Allows folks in your area to better help you. Just a suggestion - has helped me in the past.
Good luck with your trans - bummer.