This is not a full answer, but a tip on an easier way.to get to the pump. Instead of removing the gas tank. Just pull the bed off the truck! I guarantee that it will be easier. I did this on a 2001 S10 and it took less that an hour to remove the bed.
Remove the spare tire, and the tube that the tool to lower the tire goes through. You will need to unplug your tail lights under the back or the bed on both sides. There is also a grounding screw for the tail lights on each side that needs to be removed. Remove the screws that hold the gas tank filler hose to the side of the bed - right by the filler cap. Remove the tailgate (to make the bed lighter). Follow the frame down the length of the bed and you will find the bolts holding the bed on. There should be 6 or 8 bolts. My S10 had 8 bolts and my son's full size Chevy PU had 6 bolts (go figure?). Then just lift the bed off the truck. We did my S10 with 3 people and it had a camper shell and rack on it. My son's full size truck was lifted off with only 2 people. I would suggest 4 people however - one on each corner to make it easier to lift and control.
Replace the pump as described above and then you can start the engine to make sure everything works before setting the bed back on. NOTE: The fuel pump grounds back with the tail light ground. If the engine doesn't start right away, try grounding the wire back by the tail lights. It works like a charm. This is an especially nice way to do it if the gas tank is full! I spent 18 years as a professional mechanic and this is one of the slickest, least known tricks I have come across. I wish I'd known about it when I was wrenching for a living! Cheers!