The honest truth is that it takes some time to get to an ‘expert’ level where you can be confident about what you’re doing, but simply setting it up and using it for basic tasks (following some guide) is pretty darn straightforward. Most people that have issues tend to have them with use cases (eg. someone wants to edit photos but can’t get the same results as with Adobe Lightroom with alternative applications) or with specific bits of hardware (maybe they have a laptop which requires specific windows-only drivers to get the full functionality out of the trackpad, WiFi card or battery optimisation). So if you set it up and the hardware all works, you’ll probably be fine for all the basic tasks most people need, and you will gradually pick up advanced knowledge as you go along.
Mint really is simple to use. Other than the desktop (layout, look and feel), and a few changes in system apps (the backup app, etc.), you won’t need to change much about how you use it. Even the bare, raw internal config files would basically be the same (if you copied your user profile over), because Mint is Ubuntu under the hood.