well i went to replace my o2 sensor, but i couldnt get the old one to even budge.... any ideas on how to get it out?

heat it with a torch and or get the wrench on there and smack the wrench with a BFH (Big ******* Hammer.) Repeat as neccessary.

When I did my brother'* recently, which had never been changed since the car was new, over 300000 miles ago, I gave it a real good shot of WD-40, waited 45 minutes, ran the car for no longer than a minute to get it into some shade, and it popped right out.

well i tried the second part, i even had my brother try to help me... i think im gonna try the wd-40 thing before i try heat....

Liquid Wrench, let it soak for a few hours.

It becomes a juggling act w/heat. But I had just driven my car and aside from working around the heat it jumped out.

If it won't come out try soaking it in a good penetrant overnight.
Then start the car to heat the manifold a couple min.
Put a cold socket on the sensor and try loosening.
Mine was stuck and it took me two days of doing this and it finally came loose.