As far as engine goes, what part of SC do you live and what do you plan to do with the expy? I recently bought a 2000 xlt with the 4.6 and have been very well pleased. I own a powerstroke so any pulling I need, I do with it. I drove both, and in everyday driving in the peidmont of NC, I couldn't really notice the difference.
Also, finding a EB without leather is going to be difficult. Why do you want the EB? Extra options? Looks? I went with the XLT because of the price difference. It has all the major options of the EB, but without the outer trim. Interior is the same with the exception of rear vent windows that open, MPG/trip computer, and the heated/memory seats. My wife's limited explorer had the MPG and seats, kinda wished the expy did, but the price was unbeatable.
Yes, stay above the 98 year, 97 had steering glitches that ford changed in 98 and hp improvements as already stated for the other years.
BTW, I saw a 2000 Lincoln Navigator (sister to expy) on ebay today for $15,500. What a steal!