Migrating AD from Windows 2003SBS to Windows 2003 Standard edition

I have a need to migrate AD from Windows SBS to Windows Standard edition.

We have two servers, SBS is domain controller also, but 75 users are not enough. Windows 2003 SE is used as print server. The idea is to change their roles, or exclude SBS completely. Management does not want to spend money for any additional licenses (transition packs or similar), unfortunately!

Since there are no trusted relationships, does anyone have an idea how to do it?

Thanks in advance