First, welcome LaLa And, it is SO natural to be scared. Use this forum as much as you possibly can to find out about the whole process. Knowledge is power. Also, you can read about what people are gong through at various stages in their journeys and think to yourself "What will I do when I come to this? How will I best handle it?"
As far as the starch thing goes -- omg I was such a carboholic. Sourdough was like crack for me! lol! I never never never would have thought I could get over my addiction, or at least get it under control. But, here's what worked for me. I treated this surgery like what it is: a SURGERY. On my stomach. And to best protect that staple line while it's healing, you *cannot* eat things like sourdough! For quite a while. I went without the starchy things from the beginning of my 2 week pre-op diet to several months afterward, and you know what? It was like a detox. So yes, you will be putting yourself in a position where you could harm yourself medically if you eat that stuff, and for em that's what it took to break its hold on me. After your stomach is healed and you're cleared for real food, be very careful about reintroducing that stuff because by its very nature it causes you to want more.
As far as the alcohol goes... well you will need to be drink free for a while to let your stomach heal. Once you're cleared to drink, please be very VERY careful with the alcohol. Many WLS patients get into trouble with what is called a "transfer addiction" with alcohol, because it is liquid and goes down easy, and when you can no longer indulge in a food addiction it can be very easy to transfer that addiction to alcohol. Be very very very careful if you feel you may be susceptible to this. Do you have access to a counselor? if your program had you take a psych evaluation, perhaps you could see that person some more or have them recommend someone to you can talk to. If you truly are not ready, they will help you get to a place where you are.
And remember, we all had nerves about this. So we're all here to help you with yours!