Hi Tom,
Yes this would be quicker (I supposes easier is relative) using a script rather than adding loads of actions for each frame.
Whether you click the frame or a button, I'd pass the frame number to a function which would run through a loop lowering the layer value of the other frames whilst raising the layer value of the select frame.
If clicking the frame - then you'd simply modify the passed value for the called function. If using buttons, you could simply has a counter that went up and down scrolling through the images.
Mack
P.S there is an issue using layering whereby whilst the image appears on top the mouse responds to the object that is actually higher in the navigator