replacing pressure switch

I need to replace a leaking Square D pressure switch for my submersible well pump. The switch is located on a tee which feeds the tank inlet/outlet. There is no valve to prevent water from the tank form escaping from the port for the switch when I remove the "old" nipple that the switch is located on.

Am I resigned to removing the old switch and letting the tank water spray out while I try to thread the new switch setup into the port, or is there a better way to do this? I've attached a photo of the current setup. I am a rookie, so please excuse any ignorance involved with my question.

Thanks for your help.

Yeah, turn off the power first, then drain the tank.

Rancher

Is there a chance that if I drain the tank that I will have to recharge the tank with compressed air when I turn the pump back on, or should the the tank maintain the proper pressure throughout the draining process?

Turn the power (breaker) off to the pump (or just unplug the switch if it's plugged in), and open the lowest point (an outside spigot?) to drain off the water pressure.
Disconnect the pressure switch wires and unscrew it out counter-clockwise. Wrap 2-3 flat wraps of teflon tape on the threads (clockwise as the threaded end faces you) of the new switch and screw it in tightly. Transfer the electrical wire clamp to the new switch housing, and attach the wires on the screws of the new switch exactly like on the old switch. The black hot wire goes on the + side, and the white neutral goes on the - side, and the bare ground goes to green.
You won't loose any control pressure at all from your pressure tank because the air is enclosed in the tank bladder, and you're only draining the water pressure part of the tank.
Good Luck!
Mike