Garggggg 02

So I got a bank 2 sensor 2 failure alert on my 612. I replaced the rear right hand side 02 sensor on top. Thought it was resolved since that is bank 2 sensor 2. Well guess what it came back. That says to me it is the one on the bottom which requires removing the catalytic converter.

Anyone know what the book time is to replace the rear bottom o2 sensor? Tops are easy to do, but for the bottom, oh hells no