It's a very good first diesel, and last one too as long as you're not the guy that has to pull the 40ft fifth wheel 80mph up the mountain grades. They are very dependable, easy to work on, and cheaper to work on by far in comparison to the power stroke.
That price sounds rather high, but if it's as nice as it sounds it may not be too bad. As longs as it's a price you would pay and be happy with. Any pics of the rig?
The only weak link in that truck is the tranny, the E4OD was not one of Ford's better ideas. Some like it though, so that's just my opinion.