Hey Tombstoneweb,
The first step into the cold water can be hard since you are venturing outside of your comfort zone, (going from tables to div's and external css markup). This is a hard first step, and one that definately gets easier as you go. There are countless resources online for help with your css or semantic web markup. (Some have been mentioned above, but one of my favorite is the css zen garden, (
css Zen Garden: The Beauty in CSS Design)) - in the Zen Garden you will find that all the underlying source code for the web page is the same, while the css that runs it creates some real powerful presentations.
Also, for books, the css zen garden is a book, I like Bullet Proof Web Design (v2 is now on the shelves), and sitepoint's css 101 can be very useful as well when learning how to design and develop website's of any nature.
Probably the best thing you can take from leaving tables and going to the new divs / css approach is that you can easily begin to work with Dhtml in your layouts and get a more rich web interface than you could have gotten with tables, plus it is easier (for me) to mark up the DOM at run-time with a more structured approach via XHtml / CSS.
I hope this helps and it is a very exciting territory of web you are getting yourself into so have fun, don't get frustrated, and stick with it and you can pick it up very fast.
Scott Haines
Newfront Creative
San Francisco Bay Area Website Design and Development