Removal of Recalcitrant O2 Sensor

[LarryGreen]

I am unable to remove the O2 sensor from my 96 SVX. This is the one thats behind the other two (its on or near the catalytic converter). The mother wont budge. Unfortunately, in my zeal to get the thing off, I have stripped the nut. So my question is, is there any special tool, any special method, to get the thing off? I am reluctant to go to the dealer who will charge me my first born to remove it. Any suggestions would be most appreciated.