Converting HTML/Tables to HTML/CSS

While I think I already know the answer to this I thought I would ask anyway.

Is there anyway to convert and existing website with HTML/Tables to HTML/CSS? I seem to be having the most trouble with the structure itself. Placement of the different objects into specific locations. I am really confused on this.

I am not trying for an exact duplicate, close is good enough. I am trying to setup a site for selling. Problems is setting up a page with multiple pictures (catagories) a subsequent page with mutliple items within those catgories and a final page for each item.

I have looked at numerous sites for ideas and am just lost. I have aa site already developed in HTML/Tables that works fine but I want to use CSS and the site is getting old and needs a major overhaul.

I am using this project as a way to learn CSS and to get the site updated. I am not adverse to finding something (an existing template or site) that would be a close (80%?) fit and making modifications to it.

Thanks for any help.