Kerrigan,
First, you cannot copy data from one TIU to another. When you retire a TIU, you lose whatever CustomSounds and Record/Playback sessions it contains.
Second, when you renumber a TIU, all of the relationships it has with AIUs and with data in the remote, stay with that TIU. Engines added to a TIU when it was #1 are still associated with it after it becomes #2. Ditto for connected AIUs.