Exchange 2000 in an NT Network

How should I go about integrating a Windows 2000 Server running Exchange 2000 into my NT 4 network? Should I create a separate domain for the W2K server and create a trust relationship with the NT domain or do I need to upgrade the remaining serversto W2K implementing the Active Directory structure across the board? If I can leave the rest of the network as is it would be best at this time. If this is a reasonable option, what is the best method to go about doing so and where might I find somein depth technical help with the merging of the two domains?