I say you are already doing awesome, it is totally your decision and yours alone; you have to start deciding for yourself what is a good choice for you, but on the other hand if its all your thinking about and cant get it out of your head then maybe have a small one and dont deprive yourself and put it behind you. That is the whole point of this right, to start making "smart" choices, I dont know about you, but I have not been smart at all in my choices and cant believe I got here.
But, I know the feeling I have to kick the coca cola habbit, I love my soda (coke) and I used to drink so much of it. Now I have been telling myself to quite it now, so I wont crave it later...good luck with your choice and your success with the surgery.