Common elements.

I'm flying to PA today so I had some free time this morning to lounge around. As I was taking out Pixie (my dog), I found an Autozone box waiting for me on my front step!! O2 sensor is here! I had to meed Caitlin for lunch but tried to swap out the sensor before I left. No go. The old one was on REALLY solidly. I drove it for about 30m to meet Caitlin and then, with the help of a breaker bar and heat from driving, I was able to get it out. It was still really difficult though, and the new one went in just as tough. My thought is that the threads are bad or crossthreaded, but it doesn't matter now that it's in. No more engine light!!