The first thing to keep in mind when replacing the selector valve is you want to make sure the electronics function as they should. So you need to take the electronic harness that plugs into the valve loose and with the key on, two of those terminals will have 12vdc to them, when the switch is in one position you'll have +12v, in the other -12v, to verify that the switch works, put the leads of the voltmeter in the selector harness and find which two have voltage with the key on. There are 5 wires down there Brown w/ white stripe runs the gauge display on your dash, blue w/ yellow stripe I think is for the front tank sender and yellow with light blue stripe is for the rear tank sender. There is also a ground wire and then I believe it is the orange and black wires on the bottom two prongs that are "hot" with the key on. When you flip teh switch it reverses polarity to the valve which switches the fuel supply and return lines as the little electric motor flips over. If you have a Ford selector valve you won't have to mess much with the wiring. If you have an aftermarket part you may want to consider buying a Ford version as it will not fit with the stock harness and you will need to get all that wiring I just mentioned right, you'd need a schematic and the universal wiring adapter. In your case you just need to verify that the electronics work as designed(verify that the polarity switches on the harness) otherwise its real straightforward, the only real special tool you need is the fuel line removal tools. Good luck,
J.D.