Changing OUs to all users

Help! I’m in a very difficult situation with the way our Notes users have been setup. The way the OUs have been structured were all messed-up! we have about 1500 users and from what i see, the only way to correct this is to recertify all of the users one by one… Are there any other way to do this the easy way? My manager wants me to change the names of the OUs. Any idea how can this be simplified? are there third-party tools available to help me simplify this?

Ta. Allan