Yep, I was in your shoes a few weeks ago, too. My A1cs during pregnancy were 5.5-6.2, and at my 37 week ultrasound, they estimated the baby's weight at 10 lbs, 13 oz. I had a c-section scheduled for Nov 4, but my OB left it up to me as to whether I'd want to try a VB if I went into labor sooner on my own. It turned out that I went into active labor later the day of the ultrasound (10-25), so it was a very, very hard decision for me as to whether I would have a c-section, knowing that the weight estimate could be way off. When the midwife examined me when I got to the hospital, she said that it was too bad I was having a c-section, because my body was all ready to go for a VB and everything looked good. That made me reconsider and I had to make the decision all over again. :( My OB had told me that if I were her sister, she would tell her to do a c-section. And the OB on call told me that if it were her, she would definitely do a c-section. Although my baby ended up being smaller than predicted (though still big--9 lbs, 13 oz), I just didn't feel comfortable making a choice that two highly trained OBs were advising against. I do think that I could have done a vaginal birth--big babies run in my family, too--BUT I know that if the baby's shoulders had gotten stuck, and she had been injured, I never would have forgiven myself.
Just make sure that if you do go into labor and you're doing a c-section,, that you stop eating right away. I was told I could have a snack before coming into the hospital, and when I got there, they told me I had to go under general anesthesia because I had eaten too recently. Like Kristin, I agree that it's essential to start trying to accept the possibility of a c-section now, even if you keep hoping you'll be able to do it vaginally (and I really hope you can!!) With all of the hormonal stuff going on after delivery, it is really easy to fixate on what you regret about the whole experience, unfortunately, but if you have come to terms with it ahead of time, it won't be as bad.
Keeping my fingers crossed for a natural birth for you!