Well you need to have your two cameras.. Your default camera will be active.. as in the little radio button in the Inspector beside the object type name Camera.. The second camera is not active..
Then with your buttons you use the Camera Actions: Cut To Camera and Maybe Camera Fade In and Camera Fade Out..
What i do is i fade out the camera in one event
Then i use Draw Fullscreen Color, Cut to Camera, Plus any other functions i need to call to reset some menus and objects etc... in the next event
Fade camera in in the last event..
That is it.. not really fancy but it works.
Q