I didn't see anything on the GPT site that would get the file off the ECU or install the new one. That can be tricky. In road vehicles the manufacturer often tries to make that difficult. It may be easier with off road vehicles. I'm suspicious that they offer tunes for so many vehicles. Usually a tuner will specialize in a relative few number of makes. They need to test on a dyno with a vehicle to get it right. The ECU files are not generic, they're specific to the ECU and the model of vehicle.
The going rate for a tune for a car is roughly in the $500 range, plus about the same for the tuner hardware that installs the tune.
I've had some cars tuned. Some of the tunes were CARB approved, some not. When you make a non approved mod one should make sure it's possible to undo the mod.