Changing the standard Wordpress theme is very easy to do.  There are many websites that offer a variety of themes for free. Here are the basics steps to change your theme;

Choose and download a theme - Save this file somewhere on your computer such as your desktop.

Unzip the files - Can be dragged and dropped onto your desktop as well.

Upload files -  FTP the complete folder to your wp-content/themes directory. If you go back into your blog administration area,  click on Appearance to see the themes you added and select whatever one you choose.

The nice feature of Wordpress 2.7 is that you can quickly and easily change the theme at any time. Note that any modified files will need to be manually updated such as footer.php or sidebar.php files with tracking or advertising code inside it.

Tip: Choose a theme before adding tracking or advertising code!