I had GD for DD2, I managed to control it with exercise and diet. Seemed to be certain combos of things that set me off, particularly processed/prepared food which I guess is no surprise! So use the first few days to watch how your BSL's respond to different foods. Some tips I found were that cinnamon helps to even your BSLs so I added it to my porridge every breaky and yoghurt for my snack. I also found that my BSL's settled better if I had some leafy greens/vege at each meal - but watch out for the high GI things like corn/potato etc. I also found lots of fruit gave my higher readings but strawberries had little impact.
I also found that by having a snack at 10pm my fasting levels were lower - so I would have yoghurt/cheese for supper.
I was at a public hospital which has a policy of induction from 37 weeks. I managed to negotiate with the midwives and obs there to have some extra monitoring (CTG/ultrasound) and watchfully wait until 41 weeks. They agreed as I had such great BSL's and stable weight etc. I went into labour spontaneously and the only extra for DD2 was a BSL after birth and as that was fine no further action.
I hope you can get some good info re diet and exercise - I walked for at least 20mins twice a day and really feel this helped also.