^ Dont take it personally bud. Some of these guys eat each other at times too.
160k miles is nothing on the overall useful lifespan on the truck.
Those that are "into" trucks know there is a littany of things that "could" go wrong with any vehicle. Vehicle specific stuff. And there's the possibility that the current owner took great care of it and fixed all of the nuance type problems and is up on all maint and repairs.
Pulling a 5ver wont in and of itself hurt the trans, but presuming its an auto, it is also not the longest lasting trans out there. But it was good in 1999. 160k towing and stock engine, no tune, and maintained fluids filters band adjustments etc, I'd give it a greater than 50% chance or making it to 200k. On the flipside, well....
Again, it's about your expectations. Are you getting a cherry, not spent its winters in Quebec, great deal on a perfect $15k truck for $10k with the expectation that if you have to put $5k or more into it in the next couple years you're cool with that. Or is your expectation different?