I love my diesels, I really do. The power, the sound, everything about them. But... When they are out of warrentee, they are more expensive to work on. Any part pertaining to the engine is more. Water pump old truck, or Saturn cost me 25 -35 bucks. Powerstroke....$460. Starter $300, you get the picture. Big diesel in a 3/4 ford, bends the springs, causes alignment problems, and that means large dollars for suspension parts. Find someone to work on a diesel cheap... just finding someone to work on one at all is some times hard. The engine will last 400,000, but those injectors don't. How much you ask... at least $200 a piece, and for 8 of them, and install if you are not up for it.... your looking at well over $2,000 bucks. I can by a new gas engine for that.
They are fun, they are powerful, but if you are going to keep your truck a long time, and want to play with the big boys, you got to be ready to spend big boy money.
Don't buy a 3/4 Ford diesel. Get a 1 ton 4x4 with a solid front axle so you can at least align it.