there are three methods for doing this. if you have a welder and the ability to use it, i would go buy a rubber mat for the bed to cover and make it prety afterwards. you cut a hole in the bed over the fuel pump, remove and replace pump, and then weld hole back in place making sure to weld in supports for the hole. i used this method on a full sized bronco with a full 40gal tank. too big for me to drop by myself and it has carpet on the inside so it didnt matter anyways.
tank drop method:
it is easiest with a near empty tank. doable with a single person with 3/8 or less of a tank. spray hanger straps with penetrating oil (PB blaster works VERY well). remove bolts. the tankwill drop down giving you enough access to change the pump. you will need to remove the screw holding the fill tube to the fill hole in the bed, or you can remove the hose clamps that hold the hose onto the tank.
if the fuel level is high, then the ratchet strap method that jason mentioned works well. you simply use a strap in the front and rear of the tank. snug them up, then remove the hanger strap bolts. then slowly lower the tank down.
bed lift method.
Remove bolts holding the drivers side of the bed. and loosen the bolts on the pass. side. this will leave you enough room to work on the fuel pump when you tilt the bed. you will have to disconnect the tail lights on the drivers side in most cases. this method works if you have one person and are sneaky with using a jack or uing chain falls/pulley system to lift side of bed. please support it while underneath to prevent bodily crushing.
the hardest part of the fuel pump replacement is removing the ring that secures the top plate of the pump. (this terminoligy is lacking, but you will see what I"m referring to when you get there) you must use a bladed punch (large common screwdriver can work) and you'll have to tap the ring around to loosen it. the problem is that the ring is made of cheap steel and is liekly rusted and weak. I've found that if you clamp a pair of vise-grips to the tabs, you can tap on vise-grips with a hammer and this prevents breaking the tabs off. it is advisable to use an oil/gasoline resistant pipe compound to reseal the top plate when you replace it.
this is really a pretty simple procedure that will takea couple of hours if you're not in a really big hurry. since you are going to smell like gasoline anyways, its a good time to replace the fuel pump.
there are some tiny details i didnt mention here to make thigns easier, but it gives you the basics of how to do it. I assume i dont need to saym its a good idea to disconnect negative terminal to prevent any sparks, and no smoking while working on it.