First of all, there are several distributions geared for the server industry. I *personally* would not advise you to use this server in a production environment yet, but to try it out in a test lab (LAN), because (being new to this) it might be exploited quite easily.. And if the server were to be exploited, then that could put you in a difficult situation.
IMHO, the best three server distributions (in no particular order) are openSUSE, CentOS, and EnGarde Secure Linux. openSUSE and EnGarde are very
easy to use (especially the latter), so you should find yourself at home with them! To be honest, I've never tried CentOS -- but so many webhosts and people I know run it on their servers, that it must be a very good server distro
There are different lines of defence you can use in front of your server. This, ultimately, is down to you and your budget. If you could afford it (and the time to learn how to set the different the different parts up properly), then the following set up would be great:
Firewall -> Switch/Router -> Server(s) -> Backup machine on a VLAN
That stuff isn't cheap, especially if you choose the top of the range products. But, as I said, it's up to you
Ps. Welcome to LQ!!