Another command you should know about
This is the online manual. For example, to find out about the ls command, you would run 'man ls'. For more info on man itself, simply run 'man man'.
Also, I would recommend reading the DOS/Windows to Linux Howto.
It is getting a bit old now, but given your background (and attitude!) I think you'll find it very helpful.
There are tons of Linux help websites, including a specific Linux section on Google:
Also, there should be heaps of resources under /usr/doc or /usr/share/doc on your machine.
If you're interested in CLI operations (which you certainly seem to be!), there is a CLI-based file manager called Midnight Commander (mc) which can help you along. It has a built in text editor which can be very handy for quick edits to configuration files. It may not be installed on your machine by default, but a binary package for CentOS should be easy enough to find on the web.
The only other thing I can think of off the top of my head is to say that if you have any specific issues which you're having difficulties resolving, please post them here.
Oh, and welcome to LQ!