This is a very common configuration. Plenty of posts for different variations.
Basically, you use a BT connected context to trigger the profile. Then the entry task has a location -> location mode action usually set too high accuracy. A second action, app -> launch app action to open android auto.
Tasker profiles, as a general rule (unless you uncheck the "restore settings" option in the profile settings), restore the conditions prior to the entry task running. You can add an exit task to change the location mode to battery saving or whatever when the profile's no longer active (BT disconnect). Killing an app is harder, but there are methods that include backing out of the app with automated back presses (input -> back button) or automated home press (app -> go home).
There is almost too much info here on xda and across the web to start with and configure various tasks with tasker. If you are so new that the above information doesn't really help you, then it will make your life easier to start with some beginner tutorials and just practice even if you don't need/want that particular team.
Tasker Quick Start
XDA thread - TASKER GUIDE (all video tutorials will updated in this thread )
XDA thread - [TUT] The Ultimate Noob/Beginners Guide