I read from another question on here that Amazon will automatically register your user/kindle info when you order from them. If that's so, my husband bought me this as a gift and he has nothing on his kindle account. How can I change this to my account? Will I have to repurchase all books?
You can change the same from the settings option of you device. Go to the settings and update the information.
If you still face any issue, I would recommend to ask the Amazon customer care.
You can do by visiting the My Account section of Settings.