That always sucks when ya gotta sell a truck!
Youll love a diesel, be careful of the 03-05 6 liter diesels. There are some out there that have a ton of problems with teh turbos, head gaskets and injectors. Find a good one and it will be great!
If you get a 7.3 youll love it, but its not problem free. The auto trannies are weak untill they are upgraded, and you do have to do a few mods to get the same performance as a 6 liter (although it doesnt take too much)
Either way Zip, do your research and youll get a sweet truck!