[CentOS] Internet squid proxy for banner and add filtering and Nagios

Hello, I've got a standalone internet server, it's a vps and i'd like to use it for proxy and add filtering. Since it's directly accessible from the internet i need to lock it down so only designated users can get to it, i'd prefer encrypted transmission of credentials. I've also wanted to get nagios going on this box so it can monitor other services and email/sms when they go down as in an unexpected reboot and don't come back up. That one i definitely want to secure the cgi interface. For both the squid and nagios only authorized users should be able to get to them, and only users on the machine itself, via ssh, ideally should be able to configure them. I'd appreciate any suggestions. Thanks. Dave.