Has anyone done this?? if so which wire on the pcm do i tap into for the o2 sensor? or which wire on the o2 sensor should i loop into??

Check the wiring diagram for the ECM I'm not sure which way the 2002 O2 sensors are wired, but the old ones were only single wires, so it was obvious!
Get the wiring diagrams at www.allpar.com; It's worth the $25 you'll pay for it.
You might have a service connection for the guage already. I know Toyota does, but that's not much help... is it!?

Slantsixness