I just got approved...Now what?

I am a 36DD trying to get breast reduction surgery through my insurance company (CareFirst BlueCross BlueShield of Maryland). I just found out today that I got approved for the surgery!! :) The surgeon said that if he took out the required 500 grams that the insurance stated, that would put me at about a 36B (which is what I wanted anyway). Now that I'm approved, what are the next steps of the process? Does BCBS cover the whole thing, or do I have to cover part of the cost out-of-pocket? What if I get to the surgery, and the surgeons discovers that he can't take out 500 grams, will I be "un-approved" for insurance coverage? Is there anything I should do to prepare for the surgery? Approximately how long does it take for the swelling to go down and for my new size to become stable? Also, I'm a little over my ideal weight (I am 5'7" and weigh about 160). I would like to weigh about 130-140lbs, but I find it difficult and very uncomfortable to exercise, which is a lot of the reason I want a reduction. If I lost the weight after surgery, would it greatly affect my new breast size? Whenever I've changed weights before, it didn't really seem to affect my breast size (at least not noticeably). Thanks in advance for all your help!