Hi there! My name is***** would be my pleasure to assist you with this. Let's begin with signing in to your Amazon account. Please click on the link below:
Once you've signed in your should be on your account page. Please click on "Manage Payment Options" in the Amazon Wallet section of the page, where you can update your payment information.
Since you original ereader is also a Kindle, as long as you use the same Amazon Account information (email address and password) on the new Kindle., then all of your books should be available for download from your library. Please check on that and let me know the results.