The tutorials at W3Schools are a good place to get a start in XHTML, CSS and other stuff. The tutorials are easy to read and follow, and are not exhaustively involved. They are good in giving you some basic concepts.
phpNeophyte will be a great help to you as well. All of this seems daunting at first, but you will get it.
I break this down into a few major areas:
1. Basic HTML - understand the required minimum structure, and some basic rules. When moving on to XHTML, you have HTML but the rules are more strict. Since XHTML is the foundation of the web site, you must understand something about it first.
2. Basic CSS - this is a broad topic, but again, you can start with the basic rules. Don't worry about trying to learn all of the possible things you can do with CSS. Focus on things you will make your site look the way you want - coloured text, different fonts, borders, backgrounds, and the like. The rest of it will come with experimentation and more reading.
3. WordPress - again there is a broad range of things that can be done. However, I would focus on the default install. Fool around with the CSS for a while to get things looking the way you want, and when you get bored with that, then do some research. Visit some WP sites, and find something you really like. Just pick one certain thing. Examine the CSS of the site, and look at the source code. A little bit of detective work will yield amazing results and you will learn much this way. Then, if you get stuck, you can post to this forum, and ask "how do I do this" and give us a link to the site that has your desired feature or function. From there, the locals here can help you out.
Just take everything in small bites, and it will come to you over time. Don't be in a rush to build the Internet's best site; for now, build Joe's best site. The next version and each subsequent version will be that much better.