Can I get advice from the religious affairs office first before deciding to apply for polygyny?

You can, and that is a wise step before you file anything. The district or state Islamic religious affairs office usually has officers who can explain the conditions, documents and flow of the process, as well as a family counselling unit for more personal discussion. Prepare your questions in writing: what is assessed, how long the process takes, and what responsibilities will increase. Better still if you and your wife attend together, because an explanation from a neutral party often eases misunderstandings. This advice is not a decision, but it helps you assess yourself more honestly before stepping into court. See procedure by state.