I have a 2000 Excursion with 7.3 diesel, bought new. Good tow vehicle. The one thing I did that made it a great tow vehicle, I went by a 4x4 shop and told them I needed a set of F350 rear springs. They take them off trucks all the time to do lifts. They had a set laying there that they had just changed out and they installed on my X for less than $100.
We currently tow a 35' Avion trailer. X does not know it is back there. Mine has 135,000+ miles on it. We will be towing to VA for the national rally in Sept. V-10 are gas hogs. We have friends that have to stop for gas a lot sooner than we do for diesel.
Ford has 2 recalls on the 2000 that I am aware of: 1-change the CPS (cam position sensor) and 2-install a fuseable link in the cruise control circuit. Both free and only take a few minutes to do. If new to diesels, you need to go to www.thedieselstop.com
and do some reading. You will find several topics for the 7.3 engine and on down their is one for the Excursion.
Good luck with your purchase.