NT to 2000 Migration

I am in the process of migrating our small 30 user NT network to 2000 server and exchange 2000. I one PDC and one NT server. The PDC does the exchange and the server handles Blackbery services. I want to use the same domain name for the 2000 sever that I am using fo the NT server. I am putting in a new server that will replace the PDC. What is the best way with the least amount of down time to accomplish this task?