Are you sure it was DG1Z-7251-G? I tried looking that up and it doesn't show up as a valid part number. Chances are if you have the -F as a replacement, your original PTU was water cooled. The non-cooled PTU isn't exactly a bolt-in replacement. The cooled PTU has a drain plug but uses a temp sender as a fill port, and has extra cooling hoses running around. The non-cooled PTU only has a fill plug, no temp sender, and no extra hoses going to the main cooling hoses.
I kind of wish my 18 XLT has a drain plug, so I can at least change the fluid easier.