New car and trying to fix

Hey guys I have a 2004 Crown Vic p71 and I was hoping I could get a little help pointed in the rite direction, so far I can see that the valve cover has a major leak and there is a p0150 code and a P0420 code 🤢 but no check engine light any suggestions of which way I should go first ? Thx in advance oh and ps it has 275k mike 😪🤐😷

It sounds like oxygen sensor is your codes. Do you smell exhaust. Check your oxygen sensors and replace if you can. And change exhaust manifold gaskets.