When I pull my truck in for oil and fuel filter change, I usually unscrew the fuel tank cap, then do the oil change, then fully drain the bottom filter with the pet****, then proceed with the fuel filter change. It helps to get a short piece of 1/4" hose and slip it over the nipple on the bottom of the pet**** to direct the fuel into a container and away from your arm. Don't forget to cycle your key (I think the manual says 6 times?) to prime the new filters. Try this site for getting filters:
Ford 6.4 Liter Turbo Diesel Truck Filters
It's probably not worth the shipping to order a single oil filter, but you'll save a few bucks when getting the fuel filter set with it.
