Hi,Thanks for using JustAnswer.com I am Cris and will be glad to assist you.To edit payment settings on your or your wife's account. Use the link I have provided below to reach the Kindle Manage Page. Enter the email and password XXXXX with your Amazon account to log in.Once you do click on Edit Payment Settings from here you can update the credit card you want on file.
Click here>>>Kindle Manage
Also for your WiFi issue, it may be the password. If you try to connect and you get incorrect password.
Can you tell me if you have a Windows 7 computer with established WiFi connection? We can then retrieve the correct WiFi password XXXXX the WiFi PC.