how to switch camera

Yes you would need a script to switch between cameras. The most convenient way of using a switch is to keep the objects you're switching between in an array. This also makes it easier if you want to be able to switch cameras at any point. This example switches when the player presses C and a quick example of how to use it on death and respawn:

 #pragma strict
 
 var cameras : Camera[]; //Assign your cameras here in Inspector
 private var audioListeners : AudioListener[];
 private var currentCamera : int = 0;
 
 function Start () {
     audioListeners = new AudioListener[cameras.Length];
     for (var i = 0; i<cameras.Length; i++)
         audioListeners[i] = cameras[i].GetComponent(AudioListener);
     SwitchCamera(0, true);
 }
 
 function Update () {
     if (Input.GetKeyDown(KeyCode.C)) SwitchCamera(1, false);
 }
 
 function SwitchCamera (num : int, direct : boolean) {
     if (direct) currentCamera = num; else currentCamera=(currentCamera+num)%cameras.Length;
     for (var i = 0; i<cameras.Length; i++) {
         cameras[i].enabled = (i==currentCamera);
         audioListeners[i].enabled = (i==currentCamera);
     }
 }
 
 
 //Death function, for instance called when player's health reaches 0. Switches to camera 2
 function OnDeath () {
     SwitchCamera(1, true);
 }
 
 //Respawn function. Switches to camera 1
 function OnRespawn () {
     SwitchCamera(0, true);
 }

You could remove the toggle switch inside update and instead only use direct switches, if you have more cameras in your scene that should be triggered by certain events.