I got these two codes on my '08 Fit (140,000 miles) the other day. After a lot of research, I might be more confused than when I started.

It seems like these codes are the result of a bad 02 sensor, right?

But there are two 02 sensors, right?

How do I know which one is faulty?

Do I need to replace both of them?

Or do I replace one, see if the codes come back, and then replace the other if necessary?

I've seen part numbers 36531-RME-A01 and 36531-RME-A52. What's the difference between the two?

Will this upstream (More Information for DENSO 2349060) and this downstream (More Information for DENSO 2344357) work? Those are OEM, right? I definitely want to have OEM parts.

Do I need to go to a shop to get some kind of software update after/before I install these? I've seen posts that claim that has to be done.

It seems like it's something I could take care of myself, and not have to pay a shop the $500 I've seen quoted around here. But if the shop is still going to charge me to update the software, maybe I'll reconsider things.