Back Office 2000

We are currently running BackOffice 2000 in multiserver mode.

i.e. One physical server is a DC with SQL Server and one physical server is
running Exchange 2000

We would like to upgrade the existing Exchange 2000 to Exchange 2003 running
on seperate (new) hardware,
and transfer the existing mailboxes

We were originally running Small Business Server 2000 before upgrading to
BackOffice

Questions:

Has anyone tried this - is it possible?
Does anyone know of any pitfalls?
will we have to start again? I.e. install a new Active Directory
Can anyone point me to some upgrade notes/white papers?

Many many thanks in advance
Jon