My ATX also went last year, at about the same mileage. Mostly what causes the problem is a lack of preventative maintenance. The CD4E requires regular fluid changes to keep it fresh and prevent oxidation since it overheats fairly easily. Some people have gone so far as to install additional ATX oil coolers to bring the internal temperature down. You live in a very warm climate, so that combined with aggresive driving (are you guilty of lots of hard accleration, frequent downshifts?) and original fluid, and you've got a cooked tranny. It could be something small like a sensor, too. What are the symptoms?
If the ATX is dying and a replacement is in order, $2800 seems a little steep. I paid $2200 for mine a year ago and I consider that to maybe be a little high. For that kind of money, I would definitely recommend getting a second or even third opinion. And if you do get a new tranny, make sure to check the level and quality of the fluid, and have the fluid flushed every 15k-20k miles or so. ATF should be pinkish in color and have a subtle smell to it. If the fluid is brown or smells pungent then its starting to break down.
