you should be able to do this using ASA & templates as demanding said above, try testing this out with some test numbers
I would remove and then re-add, just export a list station from ASA to ensure you assign the correct coverpath & COR/COS
You will need to check what group each extension is in as these will need re-administering
It could be a good time to do some housekeeping and remove any groups that aren't used
Or you could pay a BP to do it for you and spare you the headache