I don't know what you're looking for in a truck or what's fair market value in your area, but at 24,500, I'd walk away. Here's why:
Who knows? You may want both of those things. For me though, I look at a vehicle purchase as one that has to meet my needs, but also won't put me in a situation when it comes time to sell it. I don't know what options that truck has, but it seems a little pricey for what you're getting.
If I were buying that truck, I'd need to know a lot of things. The service history would be nice. I'd need an OASIS report. Carfax or Autocheck. I'd look at the mileage vs the hours running. Check the truck over for leaks.
These trucks are a little touchy, but no more than the other brands really. If it's cared for and maintained, it should run for a really long time. First thing I'd do though after purchase is go ahead and delete what you can. Look at the pics of EGR valves and intakes and how much oil this thing can make and you'll see why.