Jimm 8/12/2012On a four cylinder engine there is only one bank - the O2 sensor 1 is upstream of the ctalytic converter (nearest the exhaust manifold) and the sensor 2 is downstream of the catalytic converter. The O2 sensors are not difficult to replace - be sure to spray (soak) the old O2 sensor threads liberally with thread lubricant beforehand. Try the 'How-To-Guides' feature on the AutoMD website for the specific steps to replace the O2 sensor.
Try the many on-line auto parts sources, such as; www.RockAuto.com or www.autopartswarehouse.com for the replacement parts.
For example, they (Rock Auto) list the oxygen (O2) sensor (downstream) from around $58.00 for your vehicle.