Please provide what Joomla release you're on as this is very vital to the upgrade process. Also please read your documentation as this includes upgrade procedures. In addition to this please review the README files included with the CB package which also details upgrade processes.
Your CSS will no longer be valid as from 1.1 to 1.4 we have changed quite a lot; you should compare the new and the old with Winmerge or something of the sort so you can see what has changed and adjust as necessary.
Please note 1.4 is latest and not 1.3, you'll want to upgrade to 1.4. You can see our progress at the forge at the following URL. Simply see closed tasks for the version of your choice.
forge.joomlapolis.com/projects/cb?jump=welcome