I have a p2195 trouble code with my 2007 Toyota Sienna CE. This is 
O2 Sensor Signal Biased/Stuck Lean Bank 1 Sensor 1.

It's a little confusing but if I am reading my Haynes manual correctly, the repair goes as follows:

 - The sensor for 2007 and later models will be in the exhaust pipe
       after the catalytic converter. 
 - To remove it, it's necessary to remove the passenger seat, disconnect and snake the pigtail through the grommet in the car
       floor. Then, disconnect the O2 sensor from underneath the van and
       replace.

Has anyone on this forum done this repair on a 2007 Sienna? If so does the above description sound accurate for how to fix it? Do you have any suggestions/advice for someone attempting the repair for the first time? Also, any advice for where to buy the replacement O2 sensor?