Migration of Windows 2000 Active Directory to Redhat

Hi,

Can anyone tell me where I can find information on how/what I should use to migrate a small/medium sized office from a Windows 2000 Active Directory domain with roaming profiles to the RedHat equivalent.   

The office currently runs Microsoft Office, Microosft Project, IIS, WebLogic, SQL Server, Oracle etc.  Migration of the databases is fairly easy, IIS to Apache is ok, Weblogic and Oracle are a no brainer.  MS Office to staroffice or openoffice is ok.  MS Project could possibly be replaced with http://mrproject.codefactory.se/.  

So that only leave the Active Directory and roaming profiles Windows 2000 Server stuff.  Any suggestions would be most welcome.

Thanks.

Later