2006 CRV error code

Took the car in as the cel lite was on.The code was po135.Car has 62,000 mi on it and I believe this was replaced once in warranty.The dealer wanted$331.85 to reoair.I stopped at Autozone and priced the 02 sensors and they said there are 2.1 was $220 and the other $500.Can I check these myself anyway and where would they be located?TIA

Took the car in as the cel lite was on.The code was po135.Car has 62,000 mi on it and I believe this was replaced once in warranty.The dealer wanted$331.85 to reoair.I stopped at Autozone and priced the 02 sensors and they said there are 2.1 was $220 and the other $500.Can I check these myself anyway and where would they be located?TIA

Autozone/Advance prices are TOO HIGH for those O2 sensors. I paid 201/160 for Bosch non-universals and even less for Denso etc. Dealer was 275