O2 sensor

I have a 97 GXE that stored code P0136 which is bank 1, sensor 2. Fuel consumption has increased considerably. Should I just change the O2 sensor or maybe the cat converter is shot. What else should I check? Oh and also, which side is bank 1? Thanks in advance.

I have a 97 GXE that stored code P0136 which is bank 1, sensor 2. Fuel consumption has increased considerably. Should I just change the O2 sensor or maybe the cat converter is shot. What else should I check? Oh and also, which side is bank 1? Thanks in advance.
Con anyone please tell me, I don't have a shop manual for this vehicle.