O2 Sensor replacement HELP (pics)

Hello Everyone and thank you in advance for any help you can give. I just went to see if i could replace my rear o2 senser myself. I have a 2001 A4 1.8T I am pretty sure I have located the o2 sensor but I have know idea on how to get to it. I lifted the car and it seems like it will be much harder to access it from underneth then it would from above. I have taken a couple pictures so you can all see what im looking at.

If anyone has advice on how best to get to this It would be apprecaited.





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Bentleys shows the 01 A4 AWM OX sensors as follows:
 
There are 2 sensors, one heated, one not. The unheated sensor is "Behind Three Way Cataytic Converter"
Both sensors are directly connected to the ECM. Both Wiring connectors are in the engine compartment on the left side.
The heated sensor has a black connector with 6 wires.
The unheated sensor has a brown connector with 4 wires.

 
How to install sensors
 
http://www.audiforums.com/m_837072/mpage_1/key_/tm.htm#849125

So I am correct in that the first two pictures are the O2 sensors? I just need to trace it back to a brown or black connection rather then that blue or green...

Thanks again for the information and help.