I purchased my 1999 in 2005 for about $15,000 with about 45,000 miles on it, and it had a 5th wheel hitch and normal receiver hitch already on it. Mine is the Lariat with 4WD, and full 8' bed, with the V-10 gasoline. Primary use was to ocasionaly pull a boat with the normal hitch or horse trailer with the 5th wheel. Does a very good job pulling either one! Gas mileage is poor, but with the big V-10 you should expect that. I only get about 10-11 mpg highway when not pulling, and with a heavy horse trailer loaded it drops down to the 8 mpg range on highway. It seats 5 with no issues and is comfortable. You do have to "climb up" into it - and ride is stiff when not loaded or pulling.
Very reliable - I only put about 3000 miles per year on mine, and have only had I minor issue, with the speed sensor on the rear differential going out - I replaced myself for $10.
Doing any work on the V-10 can be a challenge - I am 6'2" and sometimes have to use a stepladder. Replacing the spark plugs is very tough, and the year ones are very difficult to access.