Before you do too much, remember that if you select an object from the Objects or directly in the layout, you'll change the values of just that instance or instances. If you select it in the Project bar, it will select all of them in the game (globally) and change all of them. So there shouldn't be a much reason to duplicate a whole ton of objects when you can change the values in each of them as instances.
If you really are talking about clones/duplicates, then ignore this. I just don't want you to screw your project over by not being clear on instances. Also, make a backup.