Need help on how to replace an o1' QX4 oxygen sensor and parts recommendation

[AtlantaDrewQX4]

Can anyone help me get information on fixing/replacing the O2 sensor in my 2001 QX4? A mechanic told me that without even doing a diagnostic report he is 99% sure that it is the NOC, O2 sensor the way it's acting up and the mileage...and from working on so many Pathfinders and Qx4's with the 3.5 V6. I was hoping for some insight on how to replace the old with the new, what people recommend as a good OEM type product, the difference between a 2, 3 and 4 wire sensor, the tools needed and where I can get a HOW TO INSTALL YOURSELF guide. I COULD REALLY USE THE HELP!! =) Also, why the heck can't I seem to find anyone that sells manuals or how to guides for doing the replacement????