Have your dealer run an Oasis report on it. It will show all of the warranty items, plus any recalls that were done/taken care of on the truck. If it is a private party, just copy down the VIN.
My 04 has been good so far and I have 62,000 miles on it now. I have had the VGT sensor replaced once, EBP sensor twice, EGR has been replaced twice (a cleaning can also take care of it), the EGR cooler leaked and was replaced. Befor camping season this year I had head studs installed as I had stretched the head bolts (quite common in trucks with ANY type of Chip/tuner. Also happens on stock trucks, just not as often).
I tow a 13,000+lbs 5th wheel RV with mine and I have been quite happy with it. Towing I see typically 9 to 9.7MPG. Unloaded all highway at 70MPH will net me 19.8 or so. Typical commute which is 60% highway and 40% city I see around 16MPG.
Now that I bought my Mercedes 300D the Ford has been relegated to when I tow or NEED a truck to haul stuff.