You don't have to worry about spark plugs, distributors, wires, caps, rotors, ignitior chips, coils, ect on a diesel. You only need compression+fuel being injected and runs.
So if the engine is in good shape you really only worry about eventually replacing injectors. On a 7.3 that can be around 2 grand parts. Luckily they don't go out often. I recommend Rotella 5w40 synthetic as it will handle being pumped to the injectors better. The powerstroke injectors are fed high pressure engine oil to fire. So a 7.3 is harder on oil compared to other engines. Nothing to worry about, just IMO its worth buying the synthetic over the regular for about 32 extra bucks an oil change.
If/when you wear out a 7.3 (many have gone 400-500k original engine) and you still want to use the truck, don't spend 5 grand overhauling it. You could get a used cummins 5.9 and the adapter parts for close to that and have the Ford Cummins. All the Cummins goodness without the mediocre dodge.