I have a 2001 chevy silverado 1500 2WD 4.8L, that needs the bank one #1 O2 sensor replaced, can anyone please be more specific of the location. Is that the one prior to the catalytic converter on the drivers side ? Also my Haynes Repair manual sais that there's four oxygen sensors, if that is true are they the same for both after and before the catalytic converter ? Thanks .