I was pretty close on paying 3k for a 4wd truck like you describe. Good 7.3, decent body and interior, transmission was shot. Honestly given the reputation of the e4od buying a truck with a bad transmission and getting it rebuilt right, and starting fresh would have been a bonus to me..
I paid $2500 for my decent 87 6.9 with a recently rebuilt C6. The C6 made it worth it, in my mind. It was ready to go as it was, no hauling it to a shop and waiting a week or two. Especially since i drove 200+ miles to get it. I towed back the small car I drove to get it with a tow dolly.
The transmission is a lot cheaper to have rebuilt than the engine. If my engine goes catastrophically, that will be the end of this truck for me most likely, unless I get lucky somehow and get a fairly cheap ($1500-$2000) engine rebuild or swap. Much more than that? No. I could get a newer gasser. I don't particularly need diesel, I have discovered sinceI got it almost 2 years ago. I just have too much money in this truck to unload it.
I will keep it going with normal wear out parts and proper maintenance but if it needs a $3000 engine rebuild, I might just be done with it. If I go back into an apartment in the next year or two, I might put it up for sale in favor of a smaller truck, or even just a 97-200? 4.6L F150. I had a 99 F150 4.6 stepside, several vehicles ago, and it was a decent mpg truck if I stayed around 60mph.