are you guys sure that you would be best served my doing your 5th step with your sponsor? what i mean, is that you are gonna dump a lot of stuff on that person, and with your sponsor you wil have an ongoing relationship. i wouldn't want to risk holding anything back because you know you will keep seeing him, or because you care how he views you. i think i would seek out someone who has done this before, and whom i can be completely totally honest with. i'm not saying you're going to be dishonest; it's just might be a risk - i realize i don't know you.
good luck to you with it, good for you, and peace...