Ahhhh,,, The big question, what Linux to use.
One of my favorite questions to answer, so much to choose from.
Fedora Core 2 has a great installer, plethora of apps and is stable. With SELinux installed and functioning you have a major security upgrade if you can get over the small learning curve with SELinux. Red Hat has been around for a while so you can depend on them. While other Linux Distro's went commercial and closed off some its versions, Red Hat for the most part has honored open source and kept its Operating Systems available.
Gentoo is also a good choice as one of there selling points is the security aspect of the O/S. Gentoo is a bit of a learning curve when it comes to installation but you can learn allot about the guts of Linux. Also, Gentoo's package management in my opinion is one of the best. Once you have the system installed, adding new programs and upgrading is brainless. It is practically 100% automated, and if packages are missing, the package system finds and installs them for you. Basically with Gentoo, you start with the base system and then add your packages and build what you want. It is pretty simple, the hardest part is getting through installation. Gentoo has great docs online.
If you are a confident admin though, any Linux will work and if you have backup servers, support is not needed. But if you want the support and want to pay the $$$, take a look at Red Hat and/or Suse. Both distros have a huge free support base as well as great phone support. If you are going to pay for Linux, Suse's YAST configuration system is pretty awesome.
But of course distros can be debated all day long. It is ultimately going to depend on what you are most familiar/comfortable with.
As a final note:
Gentoo's forums are incredible. Answers to questions often come in just minutes. Their is really a dedicated forum group at Gentoo's site which is pretty impressive. I have always had questions answered in 12 hours or less and 90% of the time within the hour. But hey, you also have LinuxQuestions.Org with Forums for many popular distros.