Well gents, after much PB Blaster, O2 sockets and breaker bar, I could not remove the sensor. Finally gave up and had a pro remove it by heating the threads with a torch. It took him almost an hour.

Unfortunately, with the new sensor installed and the wiring checked, my O2 light remains on. I disconnected the battery for a while, hoping for a reset but still have the problem (light on, car almost impossible to start).

Does anyone have an idea on what to check next?

Really appreciate your help. Thanks.