Hi, my high mileage s70 is up for emissions and despite being in great running condition per my Volvo mechanic, looks like its going to need a new front o2 sensor to satisfy the obd. Id like to replace it myself, Ive done it on my other vehicles fairly easily but am confused about the placement of the sensor I'm looking for. In running through the forums Ive seen a handful of tutorials and descriptions but none that match exactly what I'm seeing under my vehicle. It appears I have two sensors, one just before the cat and one that appears ti be going directly into the cat towards the rear or it. Can anyone tell me if I'm looking at the correct two sensors ans if not where I can locate the front o2 sensor? Ive followed the exhaust up to the manifold and haven't seen any other possibilities.

Also, Ive read that after the job Ill have to reset the check engine light as it wont go off itself by sensing the correction. I had planned to have a garage turn it off for around $30 but have read two suggestions in the forum, one saying that the positive and negative battery terminals can be held together for 15 seconds to reset the obdurate and the other saying that disconnecting the negative battery cable for 10 minutes could possibly do it. Can anyone confirm either of these methods?

Thanks in advance for the help,
Ryan