Most real servers don't have a GUI. I think it's pretty simple, but I forgot how daunting it can be to someone who's always used GUIs. That said, there is something called WebMin that provides a web-based admin GUI to a Linux server such as you have setup. I don't use it, but I know people who do and they're generally pretty happy with it. Look around on Ubuntu forums if you need help with that. I'm pretty sure WebMin is an Ubuntu package so it should be pretty simple to install.