There are 8 bolts that hold the bed to the frame. One method is to remove the bolts on the drivers side, and loosen
the 4 on the right side. The right side bolts you loosen until the last 4 or 5 threads are holding that side of the bed on. 3 strong people can then lift the drivers side tilt it back and place a jack stand between the bed and the frame.. A better, safer way is to simply remove all eight bolts, and have 4 people lift the bed off the frame . Both of these methods will expose the fuel tank. Then you need a tool to remove the cap, you can try a hammer and an old screwdriver, but the tool cost about $20.00 bucks, and makes the job easier. I have used both methods on my 2001 Silverado. I am a veteran, on social security so I buy the cheapest pumps I can find, about 20.00 to 50.00 bucks. Gm and Delphi pumps run $300.00 to 400.00. probably more these days. Good Luck, work safe!