Wideband O2

Good evening everyone,
I am still trying to figure out how to tune my LS ECU. So, I've been reading and watching videos and still things are not clear. One of the things is a wideband O2. If I am not mistaken, a 2005 Escalade system comes with wideband O2's, so that should negate the need for an aftermarket WBO2 setup? Correct? If so, how do I use it to tune my car, where do I get the calculations/information or Lambda readings from? Could the factory O2 be connected to an aftermarket AFR gauge? Do I need to install an aftermarket AFR gauge, do I need one in each bank of my exhaust or is one ok? I am running the factory ECU recalibrated with 12587603 OS.
As always thanks to all who participate.