An help from an expert - very simple image gallery

Hi,

I need to create a very simple image gallery (see attachment).
I just want to show the thumbnails and the original image in the same page, so when the visitor click on the thumbnail the image is showed.
I have created a node with an image field with CCK, so the user can upload in the node as many images he wants.
Now I am struggling to get the layout I want.

Please could someone point me in the right direction.

Thank to everyone.