Eric, I removed my tank with the bed off, but it should be similar.
Get a floor jack or trans jack and a couple boards. Place the boards between the jack and gas tank...jack it up enough to put slight pressure on the tank. Take off the bolts holding the straps, unhook the filler neck, fuel lines, and wiring. Once everything is removed, lower the jack slowly. Make sure the tank is centered on the jack (weight wise), because if it is not it will fall off and scare the crap out of ya.
That is pretty much it. To make it easier, you might want to siphon as much gas out of there as you can...it can get heavy with alot of fuel in it.
Good luck.
