Why not use software that does the migration for you? Red Hat Domain Server is designed to fulfill the role of a Windows NT Domain Controller. The Linux Domain Controller utilizes LDAP and is designed to provide services offered by commercial directories, such as Microsoft's Active Directory and Novell's E-Directory.
RH Domain Server is an open source project best suited for medium-sized businesses, which can replace NT Domain controllers. Some of the features that it has are: a Windows NT to RH LDC migration tool, an LDAP Directory, LDAP based local machine authentication, Domain controller replication and domain trusts. For more info and/or to download the product, take a look here.
This was first published in May 2006