You will need to fit your existing styles to WordPress. By virtue of the fact that you were previously using Bravenet, I assume you aren't too familiar with CSS. For now, if you want to get your site up and running, I'd look for a simple theme with the layout and color palette of your existing site. I peeked at the source code and there is some amount of tag soup there. However, if you want to learn, there are some great tutorials on how to theme for WordPress. And that would teach you how to take an existing design, such as the one you have, and convert it to WordPress.
Most of the pages on your existing site (e.g., Services, Portfolio, References, etc.) can become static WordPress pages so that should keep things simple.
Here are some links to designing/theming for WordPress:
http://codex.wordpress.org/Theme_Development
http://www.wpdesigner.com/2007/02/19/so-you-want-to-create-wordpress-themes-huh/
http://brassblogs.com/blog/how-to-create-a-wordpress-theme