In the future always change your tranny fluid at least once a year especially when hauling and plowing. When your plowing always come to a complete stop before switching from D to R and vise versa. Saves alot of wear and tear on a tranny. Ive got a 02 f-350 powerstroke with 215,000 that is on its original auto tranny and it shifts perfectly because I always change the fluid every year and its only plowed one winter so far but its hauled for half its life.
Hopefully for your wallets sake when you get the new tranny or rebuilt tranny that it lasts you a long time!!!