O 2 sensors

You don't replace the O2 sensor without understanding the system and why do you think you need to do the job?
If you have trouble codes, it can mean a fault with the wirings or others and should diagnose and confirm the problem.

Any trouble code should tell you which sensor circuit is at fault.
O2 sensors replacement are simple plug and ply jobs whereby they are bolted on and you can remove them after disconnecting the wire harness.

There are 4 O2 sensors.

That should be simple as they are all on the catalytic converter.

Answerring owner's demand is simple but make sure it is the sensorss that are faulty instead of others because if after repalcement and problem still persists, that is the the hard part to explain.

Good luck.