I would switch to RedHat clones which are free. CentOS and Scientific linux are almost identical but may have some extra features.
The crucial feature they don't have is the full RedHat support but to make up for that they both have forums and of course still have documentation although RedHat documentation still works for both anyway.
I'm not sure about the practicalities. I think i would start by trying CentOS on a separate machine just to have a quick look around and see how familiar it is. Then try Scientific Linux to compare all 3. Then try a LiveCd of CentOS (if possible) on the main machine to check hardware compatibility, then install on the main machine as a dual-boot.
Dual-boot would allow you to reboot back into the working RHEL if you found any system that does not work 100% the way you like, and then you could do installs & configurations to get all the programs you need sorted out on CentOS done at a more convenient time for you.
Good luck and regards from