Welcome to the Forumz bud.
I myself got a '97 1500 4x4 with the 5.9. I've had it since summer of 2001. honestly, I haven;t had many big problems with it, just a few little problems. A few years ago I had to have the tranny rebuilt cause I burnt it up with an overloaded trailer while moving 750+ miles. This was at about 150,000 miles. The stock trannies are built to last and hard to kill, but once they die and get rebuilt, you can expect to have them service every couple of year. Tranny rebuild for our trucks is close to $1600 - $1800. Make sure if you do get the tranny rebuilt, to have the shop throw in an HD tranny cooler. Only cost about $75.
That's the only major thing. Other than that, radiator got replaced, top of the AC refrigerant. I've had to replace both front hubs on the wheels. Drivers side about 8 years ago, passenger about 2 years ago. Still running the stock exhaust (not for long hopefully). The engine is as strong as the day I got her. AC is cold. Honestly, can't complain about the truck. As of right now, I got close to 184,000 miles on it. Highway, city, offroad, and towing. It's a truck, and she's used as a truck.
When you go to buy it, just make sure you check the mileage, ask the owner about items fixed, replaced, etc... Best bet is to do a good 30 minutes test drive, take it to a shop to have it looked over, and most of all, go with your gut. If you seem kinda leery bout something, or something don;t sit right with ya, just walk. If after things have been checked out, and you feel good, jump on it and smile.
Bout all I can say boss.