I was told that I have 3- O2 sensors

Hello,

Of those 3 oxygen sensors, 2 of the located on each exhaust manifold and the third one after the catalytic converter under the vehicle on the exhaust pipe.
The oxygen sensors can be replaced easily. It is ideal to use a oxygen sensor socket with a wrench.
Keep in mind that the sensors have a tendency to be seized on the exhaust due to heat. It is a good idea to spray the base of the sensors with penetrating oil to help them loosen up.
Be sure that the engine is cool before getting started.

Here is a helpful article:

https://www.2carpros.com/articles/how-to-replace-an-oxygen-sensor

I have attached diagrams for each with the replacement procedure.

Please let me know of any questions.
Thank you.