Hi,
This is not a very complicated scenario if you plan correctly and execute the necessary steps accordingly. Since you are using a new server for your 2003 AD i think this would be the best option.
There are couples of methods that you can do this but the easiest way would be to setup a new domain controller on Windows Server 2003 in you ML350 and then migrate all the user accounts, computer accounts and other objects from your old Windows 2000 doman to Windows 2003 domain. This can be done by using ADMT- Active Directory Migration Tool.
For DHCP you can back up the existing DHCP database and then restore in the new server after you install Windows Server 2003.
The following links contain in-depth articles on how to use ADMT. If u like you can set up a virtual PC and then test it out before you try this on the production environment.
http://www.petri.co.il/active_directory_migration_tool_usage_w2k_windows_2003.htm
http://support.microsoft.com/kb/325379
You can download the latest version of ADMT from - http://www.microsoft.com/downloads/details.aspx?FamilyID=6f86937b-533a-466d-a8e8-aff85ad3d212&displaylang=en
Please let me know if this helps and if u need any other help on doing this. We will try to help you in any way we can.
Cheers!
Sampath