1. You can't change a IP address unless, you did something to change it...
2. You have to go to ADMIN page, to change your WPA password,
type this in the Address bar: 192.168.1.1
Username: (default is admin)
Password: (default is admin)
And, click security, and change the password all you want.
Or enless, MAC, is different. I think, its still the same way...