Quick Cisco IOS Reference
As a general word of caution, if you have no experience with Cisco or other CLI based router admin (such as linux and red hat derivatives), I would not recommend diving in unless you have a lot of spare time on your hands in the event that you accidentally delete all routing tables or cause other serious problems!
Even in a professional business environment, due to some differences between IOS and hardware versions and the need to reboot for some settings to take effect, it’s always a good idea to perform changes after hours when critical business operations will not be interrupted by internet or service downtime.
Official Cisco IOS Manual, http://www.cisco.com/en/US/docs/ios/12_3/featlist/sec_vcg.html
Manipulate NAT and other general help references and top hits on Google for common Cisco beginner questions: