Exchange Server Documentation
Large parts are very well documented. Others are not...
Please keep in mind that Exchange 2000 uses a lot of functionality from the Windows 2000 Active Directory. Exchange 5.5 uses it's own directory.
The tree can't sync when using the schema link. You can navigate to the schema definition as follows:
Enterprise Development Development Windows Server System Microsoft Exchange Server Microsoft Exchange Server 5.5 SDK Documentation Microsoft Exchange Server Microsoft Exchange Server Programmer's Reference Reference Directory Schema