Kind of a silly question but I want to be sure I’m piecing together a fair picture: both of those are five minute tasks you do yourself outside the auto parts store / driveway, right?

Accessing the air filter on the Model 3 isn't great but yes, can do it yourself. Many people just pay someone else to do things like this though.

Yes. Or roll it into a $80 service charge when you get anything else done at a Tesla service center. Like the air filters.