All I can say it try to know what to expect. The hospital you are birthing at is obviosuly experienced with vaginal breech births or they would be saying absolutely no and trying to make you have a C/S. You will need continuous monitoring during your labour (I am sure its a hospital policy) birthing a breech and prem baby but that way the hospital staff can monitor her level of stress if any and know she is doing ok during your labour. They should be prepared for something unexpected (like cord prolapse etc) and have everything in place to quickly convert to a C/S if need be. Of course there are risks but like you mentioned the chance is small just because she is breech. Being prem is more of a concern (as I am sure you know with having prems before). As for her turning it is possible but if all your fluid is gone (from the ruptured membranes) it will be harder for her to turn with no fluid to swim around in. I don't think turning a baby with no amniotic fluid would be wise but I am not 100% sure about this. Turning her there would be a greater risk of cord compression (squashing her cord) when its not protected by the fluid.
Good luck. Hope you have a good birth experience and looking forward to hearing her arrival weather thats today or several weeks away.