Volvo Repair: 2000 S80 Oxygen sensor., o2 sensors, volvo dealer

Question
I have a 2000 S80 taht I recently took to Volvo dealer repair shop and they told me that my check engine light is on because my front O2 sensor needs to be replaced. Can you please tell me where are those exactly located and the procedure on how to go about changing it? I'm pretty handy with tools and do most of my car repair by myself. Thank you very much in advance. Hoping to hear from you.

Answer
Joey, I dont even like doing these.  What the dealer didnt tell you is that there are 4 O2 sensors on this car.  There are 2 front and 2 Rears.  I dont recommend doing this yourself because you basically have to take the cat converter off to get to the sensors.  The clips that hold the sensor in is sensitive and breaks easily.  Anything on these cars are pretty much a pain.  I still would not advise you to do it but jack the car up and study it and see if you think you want to try it.  Roger