exchange 2000 to exchange 2003

I am attempting to “migrate” exchange 2000 to exchange 2003. My problem is that I find no specific information on steps to do this. I am attempting to retire an old server and wish to bring my ex2k mail information over to my ex2k3 server. Installation goes fine and most functionality is there. What does not work on mailboxes that I move to the new server is Outlook web access and shared calanders. I have searched and searched for a migration path instructions and am at a loss. Any help greatly appreciated.