I've taken a glance at Webmin and I don't recommend using it with XAMPP because of how it's set up to work. It is setup to access the debian/ubuntu repositories and they will not properly integrate with XAMPP because XAMPP doesn't install according to Debian requirements.
In other words, I recommend using the Synaptic Package Manager and install Apache 2, PHP5, MySQL server, and phpMyAdmin. It's as easy to install (if not easier) as XAMPP and will integrate better with Webmin.
As far as installing Webmin itself, it's really simple to install and I'll make a quick tutorial showing how to do so if you would like.
For great video and written tutorials and guides on creating your own web server and installing things such as forums, blogs, etc., visit http://myownhomeserver.com