Protecting System Configuration Files

What is the preferred method of protecting various selected system configuration files in SUSE 10.1 during package updates from being overwritten? For example, if I want to be sure that /etc/file.xyz is not altered during a package update install session what action should be taken? Further, would such an action allow the newer file.xyz to be placed under a different extention for later review of differences? -- /path/to/Truth