As well as the abundance of documentation provided with the operating system itself (manual pages, info pages, etc), did you check out the RedHat site?
There is an extensive collection of documentation available for online viewing and download in PDF format....
http://www.redhat.com/docs/manuals/e...RHEL-3-Manual/
As well as that, a great variety of "general" Linux documentation will prove very useful - Google for "Linux tutorial" "Shell tutorial" "Shell scripts" etc.
Browing these forums will also show you many ways of tackling various problems you may encounter.
Learning any *nix system will seem tough at first, but then, something will just "click" and everything will slip into place - and then any *nix based technology will become easy to pick up.
Enjoy the ride
Cheers
ZB