Button Help

I need help writing the code for a button that will switch the current scene.

-I want the button to be activated by the spacebar

-when the button is activated it will automatically switch the scene to another scene playing simoutaenously

-if the button isnt activated after 5 seconds it will dissapear

Could someone give me an example of what this code will look like. I am a beginner to Actionscript with very limited knowledge of coding, I appreciate all help thank you.