SES Light 3 Codes

Hi, my 2008 Versa SL has the SES light on, after a previous tank fill and it came on at the 1/2 tank mark. I've since filled the tank again (about 4 days later) and now even a couple of more days have passed and the SES light is still on.

I pulled the codes with my trusty AUTEL AL539 OBD2 Reader, and have the following Codes:

- P0137, Heated Oxygen Sensor Circuit Low Voltage Bank 1 Sensor 2
- P0138, HO2S12 Circuit High Voltage
- P0139, HO2S12 Slow Response

Nissanhelp.com info recommends replacing Oxygen Sensor Bank 1.

I am going to look under the car this weekend to see if something simple like an open harness or cut/broken wire, just in case something happened. I've had some front pipe work done in front of the catalytic but the SES light came on a few days after this work was done (replaced front pipe at dealer warranty).

My question is any other suggestions? If replacing, do I really need to get the J-38365 O2 Sensor removal too, or would a standard 7/8 wrench/slotted-socket work? Is this easy to install? What about dealer needing to reprogram?

Thanks for any advise. Btw, car seems to run fine, maybe slightly more fuel being used (hard to tell as we've hit a cold spell here in Greater Toronto Area and been minus temps for awhile now).

Regards, Ken