Going to try really hard to see if I can answer your question... as far as I know, there are not any modules out there to allow importing/exporting users with DNN.  I wrote one for our own internal use and it is very specialized to our own needs, but it is definitely something that can be done.  In essence, you'll need to be able to upload a "standardized" file (suggest CSV or TSV) and then check each row to see if it already exists in your database.  You'll need some way to uniquely identify a user in the database, in our case, we have an "employee id", though you could use email (this isn't guaranteed to be unique, however).  You can programatically add users to DNN, and there is a thread that already talks about that (http://www.dotnetnuke.com/Community/Forums/tabid/795/forumid/111/threadid/138898/scope/posts/Default.aspx)

Hope I answered your question... I must admit I am a little confused as to what you are really asking for.