Switch Camera When Game Object Clicked, and Exit with X Button

Ive Looked for this everywhere. I have made a door with a peep hole in it. I need to make it to where when you click on the peep hoe, you will be switched to a camera inside the room, and you can go back to main camera by pressing x. I have looked continuously for this, and no luck. Please shed some light on my situation! Thanks!

I would recommend checking the Camera Script References if you are a beginner.