So I went to the dealership to ask why my check engine light was on. When the mechanic came out he told me he found an LARGE EVAP VENT VALVE LEAK and FUEL CAP LEAK the code for this is P0455. Know my question is can this be just because of the cap and not actually the Evap vent valve. And how much it would be to replace because the dealership is charging me 40 dollars for the gas cap and 50 dollars evap vent valve, and with labor it all comes out to be 350 dollars. While i could probably find all this cheap at autozone. I need some opinions please. Should i go to the dealership and pay there or is it easy enough to change it my self.