can anyone show me where the pre-cat 02 sensor is? i need to replace it... and can anyone direct me to a DIY on replacing this particular sensor?

 

There are 4 sensors, two on each side of the exhaust. If you get under the car, you'll see one sensor just before the catalytic converter on each side and if you follow the exhaust pipe up towards the header you'll see a sensor just on the other side of the exhaust collector flange. I'll try to find a picture for you.

 

Here a picture. The car has berk pipes on it instead of the factory catalytic converters, but you get the idea.

 

very clear shot, very helpful on my problems