look at www.spinningbabies.com for tips to turn an OP baby in labour, and also have a look for Optimal Foetal Positioning
if baby does not turn, don;t worry! be prepared for a longer labour, with slower dilation, and avoid lying on your back. If you are able to remain active, upright and able to work with your body, you will move in a way that helps shift baby into a better position.
even if baby does not turn, there is no reason that you cannot have a vaginal delivery, it might take a bit longer !
water is wonderful, as has been said, to support you and allow you to move, whilst still helping with the pain
my OP baby turned, and once she did, my labour was very quick....but took 18 hours to get there ! but it is possible, and around 1 in 10 babies are OP, so plenty of women do manage OP births.