Agree, super easy to replace. I found them cheap online, searched on the forum and went to a site recommended by another member. Was around a $100 for both as I recall.
Found the link for the O2 sensor and they are $73 each.
Bosch Before Catalytic Converter Oxygen Sensor Direct OE Replacement, 4-wire, Heated
This tool would help.
HTTP://www.bavauto.com/shop.asp
When I went to change mine, they were so loose I removed them with no tool, just by hand.
Initially I felt better throttle response after installing the new o2 sensors.
The sensors have a suggested replacement of 100,000 which you are over.