First. What is Webmin? From their website:
Webmin is a web-based interface for system administration for Unix. Using any modern web browser, you can set up user accounts, Apache, DNS, file sharing and much more. Webmin removes the need to edit Unix configuration files like /etc/etc/ and lets you manage a system from the console or remotely.
I look at Webmin as a hybrid between a simple "finder" or explorer, a FTP and a monitoring software. You can manage your VPS and upload files and Debian updates. It is not simple to install, but it is worth the extra effort.