Replaced "rear: O2 sensor.
I too got the P0141 error code. Purchased a new O2 sensor from AutoZone: Bosch, PN 13371, cost $108.99. Here are some pics from the install.
1.) Disconnected the battery. It was time for a new battery anyway. I took out the battery first. This also cleared the fault from the computer's memory.
2.) Removed the O2 sensor connector.
3.) Used O2 sensor socket to remove the old sensor. I bought the O2 sensor socket from AutoZone as well. It was 9.99. It worked well for the original O2 sensor, but for some reason the Bosch replacement sensor is longer than the original part. I ended up having to remove the shield from the catalytic converter to tighten the new sensor with a 7/8 inch box wrench. Not a big deal, but added 15 minutes to the overall replacement. If you get an O2 sensor socket, make sure it is deep enough to handle the O2 sensor you are installing. I ended up returning the socket to AutoZone for a refund. AutoZone also has a lend a tool program where you can get the O2 socket for free with a refundable deposit. I would have done this but they were out of the loaner sockets.
4.) Screwed in new sensor, reconnected harness, replaced battery. Check engine light is gone.
In all, the replacement took about 30 minutes. It is my understanding that depending which O2 sensor goes out, you will get a different error code. The front and rear 02 sensors are different parts, so make sure you identify which one is faulty based on the error code, and get the right sensor. Hope this helps.