Or you could go to the animation palette and delete all the keyframes for just that camera. Click on the first frame in the animation palette of the camera you want to change and hold down the control key. Then move your mouse to the right to highlight all the keyframes you want to delete. Then hit the delete key. After you have done this, go to the first frame of your animation and set the camera to the way you want it. All the rest of the frames should now be at this camera setting.