Re: 7.3psd high milage question
I would only worry about the motor is SCA wasn't added to the coolant every 10,000 miles. If that step was missed, the motor is susceptible to cavitation, and I've seen a couple that hydro-locked not too far from 200,000 miles.
At 250,000 you will most likely need a new transmission if it hasn't been replaced already, or upgraded with stronger internals (torque converter is the weak point on the 7.3L). Related to that.... transmission cooling isn't as good on the 7.3L compared to the V10, so many folks install a larger cooler.
Other than that, you will have a reliable powertrain, but you may have some other chassis parts that are worn out (ball joints, sway bar bushings, radius arm bushings, u-joints are the main items).
That motor did have some issues with the camshaft position sensor. There is an open recall for it, and many drivers carry a spare. Failed CPS = no go. Also, glow plug relay is another trouble spot but if it goes out you can start the van after plugging it in for a while. It's an easy swap, and I think about $40 for a new one.
2000 E450 dually V10 wagon