I'll make this simple for you.

The issue is a sunroof drain clog. This is a common issue and several highly detailed threads are available on here as well as YouTube. Part is like 15 bucks at any dealer. However if you are uncomfortable with the repair bring it to a Nissan specialist. It could be the firewall grommet as well and I suggest you look up that as well. Once again several detailed threads on that and that is a fairly easy fix. But once again you are describing a classic case of sunroof drain clog.

Second the cabin air filter is not that big of a deal. Yeah compared to other cars it's a bit of a pain but still fairly easy. Once again several threads and instructions with pictures and even videos on YouTube. If you follow those it's less then 15 mins even taking a pee break. Just think it could be worse and some cars are worse. This is like a 1 on a scale of ten.

Third I believe you mentioned changing the oil is a pain? Very simple. I personally just remove the plastic underside protector. Takes two mins with a 10mm socket attached to a power drill. Then everything is straight forward. Nothing very hard about a spin on filter and regular drain of oil. To me the plastic protector cover is the pain for alot of people. I just remove it so I can inspect and clean.

Like I said it could be alot worse. I call a pain in the butt replacing spark plugs on my Subaru EZ30 or EZ36 engines. You have zero room and it's just better to pay a mechanic to do it since yeah it's that bad to do on a ramp in your driveway.

But once again pain in the butt and hard for one person is easy for another.

Good luck.