Exchange 2000 to Exchange 2003

I have an server that is a DC and Exchange 2000 mail server.
Because of a hardware issue I am going to replace it with a new server what I want to know is what I should watch out for with the following.
The existing Domain is Windows 2000 and the new server will be Windows 2003 and it will have Exchange 2003 Enterprise. I am planing on setting the new server up as far as possible then Migrate our old Exchange data over to it. So I am looking for any advice on what to do or not to do in this migration. Also what are my options for updating my clients to the new system (about 70). I am putting the point value high to allow for multiple answers.