OSCommerce Fixes

I need help with 3 things in OSCommerce. In order of importance, they are: 1) If a customer has an existing account and tries to place a new order without logging in, they get blocked with an error message that says, "Your E-Mail Address already exists in our records - please log in with the e-mail address or create an account with a different address." I would like that blocking to be disabled so that customers with existing accounts can still place orders without necessarily logging into their existing account. 2) When a customer gets any kind of error message after entering their address information (pages "[login to view URL]" or "[login to view URL]), all their address and contact information gets saved/remembered EXCEPT for the state, which defaults to Alabama. I would like this changed so that the website remembers all their address information INCLUDING the state. 3) On pages "[login to view URL]" and "[login to view URL]", the order of the fields is currently: Post Code, City, State. I would like that changed to the American sequence, which is: City, State, Post Code