I wish to migrate all our data from an existing (working) exchange 2003 server to exchange 2008.
Does anyone have any tutorials, clues or steps?
It's also on windows small business server, but i'm pretty sure that shouldn't be an issue.
Yes, it's very straightforward. Here is a good tutorial for migrating from older versions:
There are some things you'll have to do in order to prepare your domain for Exchange Server 2007, though:
The latest version of Exchange Best Practices Analyzer Tool, which you can download at www.exbpa.com, includes an Exchange 2007 Readiness Check option.