The migration of OsCommerce user to Drupal user can be a troublesome one, largely due to the password storage within OsCommerce. Ryan from Ubercart “the osCommerce method of storing passwords involves using “salt” on the password… appending some random characters and making an MD5 of it all. You can’t undo MD5 hashes to get the original password, unfortunately, and Drupal just uses an MD5 of the password itself” (http://www.ubercart.org/forum/development/1379/oscommerce_ubercart).
Therefore, the entirety of users to be migrated is tricky, however, a large amount of the details can be sent across as required. Merely replicate the previous steps, substituting the correct tables and column names within Oscommerce to Ubercart. If anyone wants to write a script that will do this for you, that would be fantastic, but I will leave it here as for now.