Please help, xiaobaitu and radiology and other expert. on 黨員 q

I was recommended to be a 黨員 in college by my friend, who is a student leader during my last year in college. She was trying to be helpful and thought it would help me in my job haunting. 3 years later, I left China. Now it is almost 9 years. But I did not official apply for a withdraw from the party. Frankly I do not know what status I am now in terms of this matter. Now I need to apply for EB2 based 485 and I decided to tell the truth because I do not want to lie. From posts in this forum, I guess I will get a interview. Please help on the following questions.

1. What documents should I prepare? I heard I just need to write a statement. Is that true? If not, what other documents I need to prepare.

2. What kind of questions I may be asked in the interview.

3. According to your experience, do I have a high chance to be denied?

Thanks a lot!