For documentation of how to migrate Companyweb on SBS 2008 please see the following link.

http://technet.microsoft.com/en-us/library/cc527602.aspx

This is constantly being updated from the documentation team so that should always be your first referral for information now and in the future.

Don't forget our Windows Sharepoint Operations Guide (http://wssops.saturnalliance.com.au) for information about installing, migrating and maintaining Sharepoint on SBS 2003.