Eileen...

So I had a question.  How do you move mailboxes and data from and Exchange 2000 org to a different Exchange 2003 organsiation?

Well there's a problem as there are 2 organisations so, you can't use the Move Mailbox tool to move mailboxes between different Exchange Organisations. And it's not easy either. The tool that you should use is the Exchange Migration Wizard.  You can run the tool in clone mode (run from the command line with the /m option) you may have some success... Follow the following steps;
1. Use ADMT to migrate the user accounts.
2. Identify the mailboxes that have delegates (do an LDIFDE export, or via some
other script - see below).
3. Migrate the delegate mailboxes.
4. Migrate the manager mailboxes.
5. Import the publicDelegates info into the manager mailboxes using LDIFDE.
6. Import the publicDelegatesBL info into the delegate mailboxes using LDIFDE.
Key is to migrate the mailboxes in the right order, delegates before managers. Also check to make sure the users old X500 DN is migrated as a proxy address onto their new user object.
I suggest you take a look at the following excellent reference to accessing permissions programmatically -
http://gsexdev.blogspot.com/
Also check out
http://msmvps.com/ehlo/articles/52855.aspx for a great way to help you migrate DL's.
And finally, the Inter-Org migration section in the Deployment Guide is a must-read =
http://www.microsoft.com/technet/prodtechnol/exchange/guides/Ex2k3DepGuide/37de2d3a-d42c-4a8f-af0e-c447db96dc71.mspx

Much easier to use the same organisation and use the Move Mailbox wizard...