I currently have two LDAP servers--one at an office and another at a data center. I would like to move the office accounts to the data center to centralize account management. What's the best method to migrate the accounts? Also, how do I avoid conflicting uid and gid numbers?

generally you'd just dump the data with an ldapsearch -LLL and then reimport it again with an ldapadd. As for the uid's, for a one off, i'd personally manually check before doing it, but outside of that, you can just do an ldapadd and manually change any uid's that fail, it's a pretty verbose format, and assuming that uid is indexed uniquely on the destination, it will reject those records. Note that you'e said nothing at all about what ldap services you're using, so the advice we can provide is limited.

Both servers are running Webmin so the underlying configuration may not be that standardized. I was reading the documentation on the RedHat website (the servers are running CentOS), which demonstrated how to use db2ldif, but I don't have that utility installed.

After several inelegant attempts at importing the accounts, the users are now on the destination server. However, the dn is wrong, causing them not to appear in the database. For example, "dc=hostname,dc=subdomain,dc=domain,dc=com" instead of "dc=subdomain,dc=domain,dc=com." All I need to do is remove the "dc=hostname" part and that should fix it. I wrote a file with the following contents:
then I used this command:
but I got the following error:
Nothing changed in the user list in Webmin. I tried to delete the user but Webmin times out, waiting (it tried to delete it from other modules, even though I didn't select that). What's the best way to modify the dn for these users?