I use CentOS alot for work im not sure I really like it the yum repos are old (All patches are back ported so they are secure just old) this creates problems if you want to use somithng that isnt in the yum repo like mumble. CentOS is fine for me because everything I use is in the yum repo but for you, you may want to consider using fedora because of its newer repo. While CentOS is for servers and Fedora is for more consumer home type stuff the diffrence is tiny being as they are both made by the same ppl.
Setting up a web host is piss easy if you can edit a text document with nano then you can setup a secure and fast webserver without the need of a control panel. There are generaly lots of good tutorials out there for nginx + php-fpm + apc + mysql just search google and also be weary of this bad nginx config then use phpmyadmin for your mysql interface.
Google apps isnt free anymore? Are you sure about that im fairly sure that im still using it for free i remeber when i signed up for it there was a paid version for buisneses and then hidden was a free version for personal use. Well setting up a secure email server is a massive pain in the ass if you can avoid it by useing hotmail or google or something else its worth it, if not there are pleanty of tutorials for postfix + dovecot and then just use squirrel mail for your web interface.
Their are 5 main things to do to keep your server secure.
Keep web interfaces secure.
Stuff like phpmyadmin and squirelmail are the main entry point for hackers they often have vulnerabilitys (unverified upload and sql injection are the two most dangerus and prevelent ones) are not updated automaticly and have bots scanning the net relentlessly for vulnerable versions. For userfaceing websites there isnt much you can do about this just keep them up to date, for admin interfaces however this is nice and simple just keep them behind an htaccess username and password and only use https (with a self signed cert) to access them.
Keep stuff upto date.
Second reason most servers get hacked is out of date services. This is nice and simple if you use yum to install everything just add a cron job that runs yum update -y every night.
Segragation.
Just because a hacker gets access to one service shouldent mean they get the whole server. Give each site on your server their own mysql username, password and database. Make sure each service runs under its own user one for nginx one for mysql and so on its tempting to run stuff you just installed like mumur under root but its so dumb. Run a seperate php-fpm under a unique username for each site if one gets hacked the hacker cant touch the other sites again runnig all sites under a single php user is just dumb.
Use secure passwords
Yea I really shouldent have to say this but I do, your server WILL get hammered with bots trying the username root and the password password hackers only do this because it actually gets them a lot of results. So yea your root account shouldent be accessable from ssh it should have a password over 20 characters and you should login to your server with a ssh key onto a wheel account. Also use sshguard. Some ppl change their ssh port its not really a form of security it just cuts down logs I find it annoying so I dont.
Limit the number of internet facing services/ports
IE you dont need ftp as ssh will do it with ssh-ftp so dont run an ftp service its just another entry point for a hacker. Dont have mysql php-fpm running on an open port they dont by default so you shouldent have to worrie about this but its a good concept i have seen ppl that write an irc bot that wants access to a sites mysql rather than using something like a php script that the bot connects to and then the php can clean and validate the input and give it to the mysql server they just open up their mysql server to the public the connection is unencrypted so any idiot with a sniffer can get the mysql password and have loads of access to a server they shouldent.
There is a whole bunch of other stuff you can do but this and some common sence will protect you from like 95% of attacks which is good enough for most stuff.