Hello Android Developers

I already have a Navigation Application that is almost completely developed.
now, I’d like to make this app work on Android Auto.
Of course, for distribution, I will have to do additional work to Google Auto App Guide Line.

However, above all, I can’t even see the Icon of my app in Android Auto environment.
So, I would like to ask two questions.

first, We know that Android Auto has two methods: Media App or Message App.
Should I convert my car navigation app to one of the two?

second, Can I convert my Normal App to Auto App? If so, how is that? Do official documents exist?