"This just involves grounding out certain pins on the back of the avionic shelf. It takes about an hour to do, quite simple in fact. "
You may find that some callouts cannot be simply pin-programmed. I've heard some callouts in different accents. BA's 744's used to have "Radio Altimeter" voiced at 2,500' in a very "British" female accent. If I recall correctly, Cathay had a rather unique 60' callout (which may have been critical during those old Kai Tek(Tak) approaches) which had a slight Chinese accent. Some EGPWS announcements sound as if they are spoken by a New Zealander (EGPWS systems, of course, require quite a bit of hardware/software modification).
Regards.
Q.