[CentOS] General questions about security

Hi,

I admit I never gave security that much thought, that is, except the 
most basic security rules like choosing good passwords, or reasonable 
file and directory permissions. But now I have to change that, since 
I'll soon have to setup a dedicated production server for our public 
libraries.

I wonder where to begin. I would say first thing is get a series of 
"auditing" tools such as, for example, the port scanner nmap, to test 
the firewall on the server. Any other ideas for that?

The firewall: CentOS includes a default firewall, where ports can be 
chosen using a simple graphical (or ncurses) tool. Is that solid enough 
for a web server? Or do you recommend diving into the innards of 
iptables? Or maybe, other solution, can you recommend some good 
"reasonable" set of rules for a web server, for example?

Last but not least: SELinux. For the moment I don't use it. I read the 
chapter on SELinux in "Red Hat Enterprise Linux 5 Unleashed" by Tammy 
Fox, and I simply wonder if it's worth the pain. I'm curious about your 
opinions about this subject.

Maybe some good reads on security? That is, articles that don't require 
you to be a doctor in computer science to get a grasp of the subject? 
And also documentation that doesn't require me to have a life expectance 
of 500+ years
:oD

Any suggestions?

Niki