Anything can be a lot of trouble if you don't maintain it, not just diesels. The thing about the 7.3 is its a durable engine that generally doesn't suffer from any major issues until the mileage gets wayyy up there. Stuff like injectors and what-not is dirt cheap compared to anything 6.x. Those are diesels to stay away from unless you have a real need for one, or comfortably deep pockets. I've owned or own all of them. Currently a 7.3 idi, a 6.0 F350 dually, and a 6.7 F350 fleet side. Those last two can eat you alive on repair costs.
My Ambo is a 1992 and I bought it 2 yrs ago with 104k on it. No rust on the cab, the box is aluminum, and the frame is in excellent shape. It had new tires, the tranny was recently rebuilt, and the box was 90% of the way camperized enough to make me happy. A few sensor issues here and there, probably cost me less than $100 total, and it was good to go.
Two years and 10k miles later it's 4x4, locked front and rear, rolling on 37" double beadlocks, and turbo charged.
