Then, how do I create a new Apple ID without losing everything?
Sign out of the common Apple ID, to include FaceTime and Messages, create a new ID for yourself, and then sign back in. The contents of the phone should remain intact. Purchases are tied to the Apple ID that was used to purchase them, so they would have to be obtained by the new Apple ID.
Secondly, what happens if I create a new Apple ID? You can always create a new apple id and then change to that id for your itunes account and/or your icloud account. If you download any apps with the new Apple ID, you will need to use your existing Apple ID and password to install app updates for all apps that were downloaded with your existing Apple ID.
Subsequently, one may also ask, can I change my Apple ID but keep my apps?
You can each have different Apple IDs to keep your iCloud data separate but still share the same Apple ID for purchases (Apps, music, movies, etc)
How do I change my Apple ID but keep everything?
Yes you do want this. After turning off sync individually Delete the iCloud account for the old Apple ID. Then when you then sign into iCloud with your new Apple ID select the Merge option and it will upload all your contacts and data to the iCloud account for your new Apple ID.
