Need help on how to replace O2 sensor. Also, once replaced will the check engine light automatically reset or can I do it?

 

It'll reset but you should disconnect the battery for a few mins to force a relearn of engine parameters. I think there's already info about how to swap a sensor, just make sure to do the right one and use the right kind.

 

So no splicing a new generic sensor on the downstream?

 

There is special socket for O2 sensor.
You can also try 7/8" wrench and vise grips.