Conversion from SunOne LDAP to Windows Active Directory

[Thunder]

We are a bit behind the times with respect to the authentication source we are using.  Has anyone been able to successfully convert from SunOne LDAP v 5.2  to Windows Active directory?  With or without the use of third party software?  What was the effort required and would anyone care to share their procedure?  We have thousands of users and 10's of thousands of user classes.  Also, has anyone been able to use Access Manager with Active Directory?

Thanks,