I agree with the previous answer. I will add that you can petition the court to change your last name in a separate action. You would have to file a petition to change the name and then wait for the court to issue you a notice of the change. Then you would have to publish the notice once in a newspaper of general circulation. Then you would have to file a certificate of publication and wait for a court decision.
A 12-month separation is not the only ground to use for attaining a divorce. An attorney could go over with you any other options you might have.