converting 1.3 design to 1.5 theme

Hello there.

I’ve made a design for an hosted version of WordPress 1.3 (blogsome.com). With this version, I could copy/paste my HTML and CSS in the ‘file edit zone’ and add wordpress-specific classes in my wp-layout.css (or wordpress-specific PHP commands in my index.php). There weren’t as many PHP commands and WP-specific CSS selectors as in WP 1.5, so porting a design made with custom XHTML and CSS layout was easier.

Now I’m wondering how to convert this design to an 1.5 theme (I plan to use only index.php, comments.php and comments-popup.php). Should I change my HTML/CSS to match WP 1.5 CSS selectors ? Or is there a way to keep my custom layout ?

PS: I already read some guides on ‘WordPress Codex’ which explain how to convert an 1.3 design to an 1.5 theme. But the hosted version of WP (on blogsome) seems to have different PHP commands.

Thank you in advance ,

HED