Welcome to the wonderful world of Linux (<<- is a Linux freak)! If you want to set up a server, there are lots of things that you will need to look at. I will give you a very basic roadmap to use.
1.) Find which distrobution (distro) you want to use. There are many on the market but some of the most common ones are Red Hat, Mandrake, SuSe, and Slackware. I personally am a huge Slack fan but it is a bit more difficult to set up than some of the others. Here is a good guideline to use: http://www.distrowatch.com
2.) What kind of programs does it need to run? I personally have never run a game server on Linux so I don't really know what it will entail. But one major important thing is to realize that Linux is NOT Windows and will NOT run most Windows Apps. For those apps you need to download Wine or WineX to run Windows 32 Apps.
3.) Next you need to download a distro that will work. Most are free (RedHat, Slack, Mandrake, etc. But you need to download them in .iso. Once you have an iso, you can burn them and load them. Download whichever one you want here: http://www.linuxiso.org
4.) Once it is loaded, the rest is simply READING THE HELP FILES. I cannot stress to you how important it is to do this! If you can read the help files then you can figure out lots of stuff from them.
I hope this is a good start up. The specs you listed sound fine to me. If you have any questions, just ask and I will help with what I can.