Upgrading a Linux System

My fallback system needs to be upgraded: not just the kernel but the

basic RedHat installation. (It's running RH 7.1 but a software product I need 
to work with requires 7.3.) Because this is my fallback (read: has backup 
copies from all other systems) machine, I'm hesitant to just pop in RH7.3 CDs 
and tell it to "do it."
     Should I be nervous?

--
Ed Skinner, ed@flat5.net, http://www.flat5.net/