As a member who (after 23 years of continuous sobriety), went from gullible newcomer to AA lawyer to bleeding deacon and is now more agnostic than anything else, I can empathize with where you're at. The real key for me was not assuming that the "spiritual terms" all mean exactly the same thing to everyone. But the human tendency for rule-making is a strong one, and people who are terrified of dying drunk are just as dangerous as people who are terrified of dying at Armaggeddon.
You've gotten a lot of good suggestions here. I'd like to add that, as a serious agnostic, I recognize that my "spiritual experience" is mostly the result of chemical and electrical reactions in my brain, and that these things have happened because I changed my behavior, creating new pathways for the chemical and electrical responses. Cool. I actually know how it works. But the real "how" is in changing my behavior, which, for me, starts with my attitude.
We change our minds all the time. The important thing for me is developing the very necessary ability to tell others--AA members or not--"I really appreciate your concern and the affection you're showing with the advice, but this is where my path is going right now." For example, I'm in a spot now where I'm exploring Buddhism, but most of the meetings around here have a real Christian bias (most meetings in general do...it's a failing of AA, and a great reason for more research into the treatment of alcoholism). I've cut back on meetings to do other things, and have had a great deal of concern expressed. Because I'm willing to believe that the concern is real, and that the reason people are afraid is because they're afraid of losing their own sobriety, I'm able to say, "I'm investigating some new approaches to my spiritual life. The Big Book tells us there are many approaches--I'm just checking it out."
As for Step Three, my understanding of that step has changed so much over the years. At one point, it was simply to make sure that I wasn't the only source of information for my decisions, because my thinking has historically been trapped in fear and selfishness. I did get into some trouble with "turning my will and my life over" to a sponsor--BAD BAD BAD, but I learned from it to never abdicate responsibility for my own decisions (you'd think I'd have already gotten that, thanks to the JWs, but live and learn). EDITED TO ADD: If you're not comfortable with this sponsor, change. It's not like you're married, for goodness' sake. But you might also consider that the Big Book has the option of using your own words for the Third Step "Prayer." Try that on your sponsor, and see if you can't come up with something that works for you. Remind your sponsor that it has to be your program in order to stay sober, and make it yours. The key for me has been to ask myself what each step means for me today, where I'm at now. It's the underlying principle of the step, not the letter of the law, that keeps me sober.
For me today, Step Three is mostly about understanding that I never have all the answers. Ever. But even though I don't know what I'm supposed to do, I know what not to do, and once I've eliminated all the selfish, dishonest and fear-filled options, I'm usually left with some pretty decent choices.
How do you know it works? If you don't drink, you get along better with other people, and you can stand to be around yourself, it's working. And so far, it's working for me. Hang in there, digeridoo.