The O2 sensor comes up through the floor panel on the passenger side.
1) Make sure car is OFF.
2) Remove passenger side seat.
3) Remove kick panel (under the glove box)
4) Remove carpet fasteners
5) Remove carpet
6) Jack car up
7) follow the o2 sensor wiring you need to replace up to where it goes in the car.
8) wires go through a grommet
9) Push grommet through and replace o2 sensor.