I still have a 99 and 02 7.3 with the ZF 6spd manual trannies which I bought new. Chipped the 99 and bought a programmer for the 02 which I never put in as it came stock at 275HP. If it's a auto tranny I'd add a extra oil cooler and all the engine needs is a new radiator cap... seriously. Look to see if it has the camper package as it adds a rear sway bar and the extra helper spring... same as a F350. 3.73 rear axle is great and you can pull in OD with most loads. The turbo's butterfly can be tricked into being a very good exhaust brake, even with a auto tranny.
There is a reason it will cost more than a newer 6.0 PSD POS. I am thinking about selling my 99 extended cab 4X4.:W Hopefully the 6.7 will be as good as the 7.3.