help! how to remove high pressure switch

[finngal]

I have a 1998 V6 Toyota Camry. Air conditioning won't hold a charge - there is a leak right below the high pressure switch, above the nut. I was told there is an O-ring below the switch - does this maybe need to replaced for a buck fifty? Does anyone have experience with this? The nut won't budge - how can I get the switch off (without taking it to the dealer who wants to charge 240 bucks when the switch costs only $43!!!)?

[toyomoho]

Toyota states to put a wrench on the body holding the sensor to prevent damage. Use another wrench on the sensor. No other special requirements were mentioned. Keep in mind the A/C system needs to be discharged if the valve is changed. If not, the Freon will come of the hole the sensor screws in to.