Where are the O2 sensor located on a 2000 VW Jetta VR6 and are they easily removable?

I just replaced both O2 sensors on our 2001 Jetta VR6. I was able to remove both using an open-ended wrench since I didn't have that special tool, but it's a bit hard to reach since both are located on the top of the converter-one at the input (near engine) and the other at the output (toward the rear end). I would recommend changing one at a time so that you don't accidentally swap them (front to back). A dealer told me to tighten gently (like a spark plug--no tighter). You might get an Check Engine light after working on the O2 system. That would need attention by a qualified person (maybe you!). Some parts distrributors such as Autozone, Advanced Auto etc can check for diagnostic codes that light-up the Check Engine lamp, and they can also clear those codes too. Not sure of exact location in that model, but one will be located in front of the catalyst - usually at the base of the manifold or just in front of the catalyst. The other will be just behind the catalyst. Fairly easy to remove. You need a special wrench or socket specifically for O2 sensors, about $10 - $15. ------------------------------------------