Microsoft has a document. If you Google [ gettingstarted_combined.doc ] it will point you to the link.
Here is another link to some docs [ http://www.lwcomputing.com/tips/static/sbs.asp ].
I would caution — SBS2003 support will sunset in July 2010. If you are looking at a first install and haven’t yet purchased the software, you may want to look at 2008.