If there is no other court proceeding pending, you would follow the same statute and file a petition for name change. A name change can, however, be received in some family law proceedings like a divorce or adoption.
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There is no "reversal" of the first order changing your name. That is, you cannot reopen the case and ask the court to vacate the order changing your name. You can file a new name change petition and ask the court to change your name to any name you want, including the name on your birth certificate.
In WA, the name change petition is filed with the district court where the person lives. In some circumstances, such as the petitioner wanting to seal the petition, the petition would be filed in superior court.
Since you already did the petition once, you should know how easy the name change petition is in WA. There usually is no need to hire an attorney for a name change petition. If there are special circumstances, you can hire an attorney to help you.