Uhh, big crescent, or a wrench that fits should do the trick. Especially if your stock fuel bowl is out of the way.
Take the nut off the back carefully. Unplug the solenoid and secure the wire so you don't drop it in the valley (especially important if you have dual pumps).
Slide off the solenoid and carefully set it aside.
Should be able to easily unscrew the valve itself at that point.