my 2nd baby turned breech at 39 weeks and then turned back again a few days later, was born head first at 41 weeks with no problems at all, pretty easy labour actually. so don't panic, you've still got tonnes of time for baby to get head down. also, with subsequent babies they don't tend to drop and engage until much closer to labour and they are usually more able to turn around if you've already had one baby since the muscle tone of the uterus will be slightly weaker.
there are plenty of things you can do to encourage baby to turn, i did everything i could so i couldn't say which was effective, i'll post some links in a minute...
when i was looking at the possibilty of having to give birth to a breech baby my midwife told me that since i'd had a baby before they would let me try a vaginal birth if i wanted because there are less risks/unknowns but i think that's something everyone has to assess for themselves since c-section is by no means risk free. at least you have plenty of time to research your options
good luck, and i'll send baby turning vibes your way