finally got the trans failsafe program

[imsello]

on my 04 4.8is. tranny had been acting up for a while it has 120k on it so its not something i didnt expect. but this is the first fail safe progrm code. but when i shut the beast off it went away and didnt come back on..is this the sign of the tranny gettting much worse,,cuz honestly it wasnt that bad before, id figure id drive it until the tranny just wouldnt shift anymore. but today it dropped a gear on the higheay and sent the rpms to like 6500rpms. id much rather repalce the tranny than the motor. so i think its time. anybody know where to get a remanufactured tranny with a warrnaty for this beast. i actually got a pretty good quote before from the tranny shop for a BRAND new unit from zf.. he said like 5200 for the tranny does that sound to good to be true. and hes telling me like 500 for the fluids..should i get them myself and will it save me money to do so and where whould i get the fluid from? any help would be greatly appreciated.. i figure with a new tranny this truck will last a lifetime or at least until i have to get a new tranny..