Anyone know if i need to replace the bearings while i'm doing the Rear brakes? What is the name of the abs sensor inside of the rear disk? Do I need to replace this as well?

thanks

The ABS ring you refer to can be removed and swapped over to the new rotor.

There are 2 bearings, an inner and outer. Replace them both.

Once you have the rotor and bearings removed, I use a long screwdriver and poke it through the front side. Some light tapping with a mallet will loosen it.
Just work your way around the ring, it's just slip fit on the rotor.