I just changed the fuel pump on my 99 suburban 6 months ago. I also thought
I could change just the fuel pump, but found that I needed to replace the
whole sending unit assembly. It was pretty easy, and it also took care of
the problem my fuel guage was having (not reading anywhere close to
accurate). Also, you might want to consider replacing the pigtail
connector on the truck side of the electrical connection. I had to pull
the tank twice more before I found this probem, and the guy at the
dealership had the part number memorized. About $300 for the fuel sending
unit, and $40 for the pigtail connector (as far as I can remember).
Hope this helps.