As for brakes -- don't forget them. I had to replace mine at 37k miles (bought truck with 29k miles). Had to replace rotors, since one pad had worn through on inner portion & chewed into the metal. Installed powerslot with heavy-duty Hawk pads. That really made a positive difference in braking ability -- I am still glad I was 'forced' into this mod.

 

My brakes (same truck) went 60,000 miles and had some life left. Something really wrong to only last 37,000 miles.
The main thing would be to change oil & filter (5w20 and Motorcraft filter), have the tranny powerflushed (did mine @ about 55,000 miles), change the coolant (did mine @ 50,000 miles) and inspect the brakes. The differentials have synthetic fluid in them and should be good for at least 100,000 miles.
The front differential does have a fill and a drain plug.
I have just under 64,000 miles on my 01 and have had no fluid related problems at all.