Stokes interviews are for conditional permanent residence not to remove the condition. In any event, I think you should bring in a lawyer. CIS isn't there to help you and they certainly don't do things with your best interest in mind. You may have got an interview solely because it was random or perhaps becuase you didn't send enough or the right documentation when you filed your I-751. If you've been collecting good evidence and have joint tax returns, bank statements, pictures, bills, etc., I would still bring a lawyer with you but you should do fine.
A second interview usually means CIS suspects fraud in the marriage. You should consult with and consider retaining an attorney to represent you at that interview. Critically, you want to avoid having CIS determine that the sole reason you married your husband was for an immigration benefit. This is called a 204(c) finding and permanently precludes you from obtaining status through any family member.
Seek counsel immediately.