Be sure to take photos of any error messages so that you can show them to the mechanic. Make sure that the outdoor temperature is also in the shot. I would take a photo each time it happens even if the message is the same, that will show the frequency that it occurs.
As for the maintenance minder messages, the "A" code for oil change seems to come on when the tire rotation (code 1) comes up every 6,000 miles or so. Many people ignore it especially if most of their driving is EV, as there would be very few miles on the engine at that point. You can clear individual codes by going into the "wrench" screen on the display which is controlled by the button on the steering wheel. What many people have found (including myself) is that when you clear the tire rotation code only, the A and 0 codes also go away. The owners manual says to not go more than a year without an oil change so many people (including myself) just change the oil once a year and ignore the "A" code whenever it appears.
The "0" inspection can be pretty expensive and there is a question about whether it's really needed so soon on a new car but that's an individual decision.
Cabin filter is easy to check and change yourself, there are Youtube videos that show you how. I haven't changed mine yet but I have pulled it out and inspected it. When it's time to change you can find cabin filters online for a low price.