[COSVT03]

Hit the ceramic part of the old O2 sensor with a hammer...break it off, cut the wires, then you will have much more clearance to get a short socket and breaker bar on there. Make sure you use a 6-point socket.

THIS IS A VERY BAD IDEA - If the sensor is SOL and WONT come out, you now have a hole that needs tooled for a plug or some work at a muffler shop to remove and weld on a new bung. IMHO

PB Blaster is a great one, they also JUST came out with a PB Blaster Freeze product that works AMAZING as well... I love PB

PB- tap lightly - wait 10-15 minutes (MOST IMPORTANT PART IS WAITING) repeat up to 3 times.
Typically when replaced every 50k - they don't rust in place and are easily services. But, that isn't the case usually.