The important thing about doing a 1st Step, IMO, is to leave absolutely, positively no room for doubt. Don't leave a door or window open, even a crack, ya know?
I did a couple of things for my First Step. One was to write out long hand my drinking and using career and to read it to my sponsor. I also did the NA workbook, which is very thorough. And last, I read the BB and 12x12 first step and shared about it in meetings.
Consult with your sponsor on this one, like you said you are going to do. She is the best one to advise you.