Will “Oracle Express 11gR2” installation mess with the "Opera PMS" software
It's hard to know what new software breaks prior to testing it out on your system, so it's just best to create a Recovery Point on your PC prior to doing so to be safe.  After you create a manual Recovery Point, perform your install, reboot, and test stuff out.  If you feel dependencies were affected and you're unable to resolve them, you can always recover your system back to the recover point, effectively rolling back the installation (and any damage it caused).