[Nodnarb76]

I have done this job a few times on my Suburban.

Support the gas tank with a jack. The gas tank is held into place with two metal straps. Remove the two bolts at the front of the straps (please make sure gas tank is secure). You should then be able to move the straps to the rear of the truck and out of the way. lower the jack/gas tank just a little to be able to get to the top of the gas tank. Remove the negative ground lead for the fuel pump it is bolted to the frame. Unplug the fuel pump connector. remove the fuel filler and vent hoses, fuel supply and return lines.
After everything is disconnected should be able to lower the tank out of the way.

I took a pic last year when I was doing this job. Hopefully the pic may help too.