Can someone tell me where the 2nd o2 sensor is on my car. I haven't been underneath yet, but i know thats where it is. Just trying to figure out which side of the car to go under from. I replaced the one in the manifold just under the rear valve cover. Need to replace the other also.

 

You have an O2 sensor on each of the exhaust manifolds, and there may be two at the catalytic converter...one in front on the early production models only("pre-converter"), and one to the rear("post converter") of the converter on all.
Are you getting any codes that would point to a specific sensor?