Where are the oxygen sensors located on 2001 Montero sport?

Looking in under the hood, The first sensor is on the left side (pasanger side) under the spark plugs near the rear of the engine by the firewAll. It will be sticking out and looks very similar to a spark plug. It will have a wire connected to it. From the same view you can see the CAT converter. The second sensor i guess is after the CAT converter and is mounted horizontal. I recently took my montero in to auto zone for diagnostics, it gave O2 errors. Im not sure which sensor is bad or even if they are the same. If anyone has any answers or suggestions, email me at stevejlack@hotmail.com