When you upgrade by unpacking the new archive on top of your old installation you will potentially lose:
- modifications to the default styles.
- modifications to the template files.
All other files, posts and settings will remain. So, if you want to be on the safe side, make backups of your styles and template files before you upgrade.
As far as I can see, you haven't modified your template files or any of the default styles in any way, so that won't be a problem. What you will have to do though, is to update the style "sc02" so that it will work with 1.0. I took the liberty of doing that for you:
http://punbb.org/stuff/sc02.css
This is how it should look after you have upgraded to 1.0.