Howdy,
It’s absolutely possibly to install the Virtualmin module on an existing live server (though, not using the install script – running the install script on a live server is bad
The advantage of installing it on a newly installed server is that the install script configures a boat load of stuff for you – Postfix things, procmail things, Dovecot, SpamAssassin, the Virtualmin repository…
All things you’re able to do on your own, but it saves you all that hassle – but also sets it up in a manner it knows how best to work with.
What you’re saying, though, is that you have a domain that works. That means you already did a lot (though probably not all) of the hard work
If you were to install the Virtualmin wbm module (and the coinciding theme), nothing on the system would change. That is, it’s not going to run around changing your config files, it’ll use your existing setup.
If you were to go here:
http://webmin.com/vdownload.html
Skip the paragraph about using install.sh – just after that is how to set things up without using the installer, and instead directly using the modules.
Again, it may take some tweaking to get it working ideally, but installing the Virtualmin wbm module itself is harmless, the trick is configuring the rest of your system in a manner that allows you to fully utilize all of Virtualmin’s features.
Does that answer your question?
And remember, don’t run the install.sh on a live server, we’re just talking about the standalone modules here
-Eric