Hello, so I got these two codes after most recently scanning my car and I was wondering if it is really just as simple as replacing the oxygen sensor after the catalytic converter or would it require more diagnostic to actually see what the problem is? Is that an easy DIY fix? Also, I have a small little oil leak and was wondering if this could have anything to do with it? Thanks!

2011 Mini Cooper s. Stock except NM power module on low

2D22 - oxygen sensor after catalytic converter. Electrical: line disconnected

2779 - hot film air mass meter, operating range: period duration too low, air mass too high