Slow down, deep breath. First, download whatever themes you like that are "closest" to what you want to do. I can only assume you are using v1.5, right???? Of course right.
Okay, upload them to your "wp-content/themes/" folder on your host server (website). Pick the one you want to work on and activate it in your Presentation Panel. View the site and click everything to make sure it is working the way you want it to work. All the categories are looking okay, the single posts, etc.
Then, when the Codex is back running, any moment, check out the instructions at:
WordPress CSS Information and Techniques
WordPress Blog Design and Layout
Using WordPress Themes
Developing WordPress Themes
And they will tell you just about everything you want to know.
Basically, you start from one theme and then make changes in the CSS file (style.css) to change things like font colors, layout looks, images, whatever. These links will help you totally.
And when you are ready for a test drive, post a link to it in "Your WordPress" on this forum and we'll take a look and comment, smack you around a few times, hang you by your fingernails, and be abusive, but really nice while we are doing it. ;-) Good luck.