Does anyone know exactly how I can troubleshhot the problems with these codes. I've already changed the gas cap after Autozone said the PO442 code showed up. A day later the light came back on. Replaced fuel cap again with no success in keeping the check engine light off. Then Autozone said there was a small leak and a big leak in the evaporative emissions system. These are the codes they pulled up today. I have a print-out from Auto Zone with very brief details on what the codes mean.

Does anyone know what I need to check or replace?