when picking up a used vehicle, especially 15-yrs old or whatever, always a good idea to change all of the fluids out. FT/RR diffs, Tcase, new Filter a Dexron6-synthetic for the trans, 5w30 dexos synthetic motor oil, coolant, flush the brakes & power steering, lube all of the chassis grease zerks (15 or so) new spark plugs maybe wires too, rotate the tires & have wheel alignment checked along with front suspension/steering, replace PCV valve & fuel filter. Inspect the brake pads as well, Get any fault codes squared away i.e. "check engine"
That truck is a BEAST & those wheels look awesome on the white paint scheme.
I bought a 2003 and did 2 or 3 maintenance R&Rs each week until everything in it was fresh. Hopefully it keeps going another 125k
Do you know the previous owner or have the maintenance history?