I filed I-130 for my Dad, who is living in China. Recently I received the approval notice of I-130, and an envelope containing both AOS processing Fee Bill Invoice and other documents, such as, Choice of Agent and Address Form (Information about the DS-3032),etc.
From my understanding of the DS-3032, it seems like that I should be chosen an Agent by my Dad considering the difficulties encountered with international mail.
-Your father does not need to hire any lawyer, but use you or your spouse as the person for the communication between your father and the national Visa Center. So, just fill your name or your spouse's name and your current U.S. address in the DS-3032.