I've created you a FrogCode Widget which does everything that you need it to... I say "need" because due to time and technical limits I have not been able to implement transition effects (fade in/out).
When you come to use the widget, make sure it is on the first page of the site only... this is important. Once on, it will be invisible when the site is live. In edit mode, you will be able to set a time in seconds for how long each page is visible before it proceeds to the next page. The last page will wrap back to the beginning.
If you need any help installing this widget, let us know, otherwise you should be good to go!