Transitioning from one Camera to Another

I'm guessing that probably many people may have asked this question, but I was wondering how I could to program a script that changes the camera following a player (in my case a sphere) to a camera placed in Bird's Eye view?

I used the scripting in the tutorial for Roll-A-Ball for the main camera following the player and would like to somehow integrate the script to (possibly lerp or) move to the Bird's Eye view. I want to use the Spacebar in order to toggle from one camera to another. If a seperate code would be needed, that is also would be fine by me.

Thanks for any help possible!

P.S. If it is also possible, could anyone also tell me how to disable player movement when the Bird's Eye View is activated?