You won't have any milk yet - just the beginnings of colostrum.
Your breast milk will come in a few days after the baby is born.
But by this time, women often experience drips of colostrum from their nipples. And green is a normal color. Not quite sure why your doc said what he said - in the future, since you're uncomfortable talking with him about your health because he is a man, is there a nurse in the office you can discuss your concerns with?
As above. Dripping colostrum is normal at that point. It is often a white off white, but I think been is normal too.
You have no milk to express, it would be a waste of time, and yes it can cause labor. If you plan to breastfeed and haven't already I highly recomened you try to fine some kind of class on the subject. Out off all the things I read or all the classes I went to before giving birth a breastfeeding class was by far the most helpful. Breastfeeding while well worth it isn't as simple as it sounds.
Please don't start expressing, it can cause early labour! With my first the midwife explained that by expressing you are tricking the placenta by sending it signals that the baby has been born and needs the breast milk x