The sending unit is in the tank and accessed from the top of the tank. You most likely will have to drop the tank to get to it. If you are real lucky you will be able to see it mounted on the top front edge of the tank and be able remove it without dropping the tank but in any case you will be under that truck.
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles