I have a transgo and mine is a gt so the trans works a little harder. It has been fine with no problems whatso ever. It was not extremely difficult but install is a cost you have to consider. I got mine off ebay new for $90. I would suggest just getting a programmer/ chip and have them firm the trans up that way AND get some more ponies under the hood. two birdsne stone!
Takes about 2.5 to 3 hours for a transgo @ 60-75 an hour. If you know absolutely anyone with a little know how on trannies they could help you out. they are not hard, just time consuming. I had a ford Tech put mine in. We had a lift and everything and it still took 3 hours. he is very picky and triple checked everything, though!