It's inside the fuel tank, you need to drop the tank in order to gain access to it.
You can also pull the bed off. This is actually the easier option because you will easily have access to the top of the tank and all the fuel lines. TO remove the bed, you must remove the 8 bolts (nut side down) the hold the bed on the frame, the 3 screws that hold the gas cap fill tube to the bed side, and the 6 clips under the tail gate that hold the wiring harness on, also disconnect the 4 wire connectors (1 to each turn signal and 2 to the liscense plate lights. All in all with air tools this can be done in 1/2 hour and 2 to 3 people to lift the bed off. It is not heavy relatively, but it is a little awkward.
to remove the fuel pump you will see a round black piece (likely badly rusted) on top of the tank, it will have 3 metal lines comming out of it and some wires as well. You will need to disconnect the 3 metal fuel lines, the wire connector, and remove the 7 Phillips head screws. the fuel pump bracket will lift right out (It may actually stick a little if the rubber gasket is corodded just pry around it to loosen and then pupp it off). The fuel pump will be near the bottom, and looks like a small electric motor.
It would be adviseable to replace the entire pump and bracket assembly as well as all 7 screws and the gasket if at all feaseable. the brackest and fuel lines are known to go bad. Unless you find one uese these are a Toyota only item and wont be avaiable at an autoparts store. If you shop around some dealers offer substancial discounts Toyota of Dallas (TRDoffroad.com) the whole kit will cost between $130 and $180.
Good luck, now go do it don't be scared. SOme forums for additional help: toyotanation.com, yotatech.com, pirate4x4.com. there will be several people on these forums to give you extra tips and encouragement. Pirate is for a little more advanced users so tread lightly there.