Standing in front of the car, and looking at the engine, bank one is next to the firewall, so sensor one for bank one is back there in the exhaust and before the cat. conv. Bank two sensor one is up front next to the radiator. NOW: if you dont have the proper tools and skill level
and know that the sensor is actually the problem, let a Mechanic check it out so as not to waste your time & money.
A code does not mean a certain part/sensor is defective! A sensor detects/senses a problem in a certain area, so you know where to start testing, not replacing. And the sensor may be bad!