Restore previous version of an app

Hi

I've had my MacBook Pro for a week and already they have released Safari 5.

I've downloaded the image to install it - it is sitting in downloads. Before doing so a question.

If for whatever reason I wish to go back to Safari 4 as supplied do I just restore that application from a Time Machine backup or do I have to delete/remove the new Safari install first then restore 4 to a none existent/empty location. Thinking about restore not removing all of the 5 version if there isn't an equivalent file in the 4 version. Is restore a package restore i.e. replace the existing package completely.

Does that make sense?

Thanks

You will not want to go back to 4 !

I installed 5 and yes it is fine. But my question remains - if I wish to revert to ANY application I update "Is restore a package restore i.e. replace the existing package completely".