There are a number of scripts you can use. This one is very easy:
http://visuallightbox.com/
It creates thumbs automatically, but it would require the use of XHTML at least on that page, so you can only use it with NOF11.
Lytebox is also OK:
http://www.dolem.com/lytebox/
You'll need the pictures in a small and large version. You include the scripts in your local publishing files. In order to build in the gallery you would have to do what they describe on the Website:
Add the code between head-tags in your master-border:
Code:
<script type="text/javascript" language="javascript" src="lytebox.js"></script>
<link rel="stylesheet" href="lytebox.css" type="text/css" media="screen" />
Add ../ if the gallery runs on underpages (not on opening page):
Code:
<script type="text/javascript" language="javascript" src="../lytebox.js"></script>
<link rel="stylesheet" href="../lytebox.css" type="text/css" media="screen" />
Now insert your thumbs directly on your page and link them to the enlargements. Add the following information in HTML > inside the link):
Code:
rel="lytebox" title="Image Description">Image #1</a>
You have to try around a little bit. Sorry I don't have an english nof-version here, otherwise I would make a few screenshots. Maybe somebody knows a tutorial in english.