sorry but this is kind of question a good hoster never ask.
you don't really want to host sites, do you? it would just lead to immediate crack of the entire system by some cracker. learn basics of unix-systems first, then go make a hosting playground.
at this point it just can make more troubles than actual help.
when you get into basics of linux, security and running servers, you can come and ask real question about some problem you experience and can't solve.
about distros: i can recommend Debian. I use Debian Lenny pretty long time and find it good as server system. It's a good place to start for a novice user willing to be a kind of hoster, to run some servers.
about cpanel: consult the manual. sure it's pretty well-documented.
p.s. just remember: linux is not more secure than windows if it is run by someone who doesn't know how to protect it from crackers.