I really understand what you're going through. I had my daughter 4 months ago after being diagnosed with GD at 29 weeks.
As I controlled the GD with diet, they were going to let me go over my due date no probs (baby only weighed 7lb 1oz at birth). BUT I had a bleed the week before I was due so was induced on her due date.
I knew she wasn't ready to come out and the induction didn't work at all. Not even 1cm after 24 hours and waters broken! However, this was not why I had a C Section. The bleeding returned and it was considered an emergency.
Sooooo I did have a C section (which I was dead against), but it wasn't really anything to do with the GD.
On the positive side, you get treated really well and my consultant was with me all the way. She even performed the operation and I felt really well looked after. Recovery was surprisingly easy and I still managed to breastfeed no problem.
Everyone's birth story is different so try not to worry. I know there is a higher rate of C Section, but I think that's mainly because they don't like you to go too far over your due date. If you control the GD by diet, they'll be more likely to let you go over.
I was induced (by ARM only) at 39+3 as they thought ds2 was big (9lb8 but not that much different from my others) and to be honest my previous cs was much more of a concern to the staff than the gd, they wanted me to eat at regular intervals and check blood glucose but that was about it. Labour ended in cs but because of complications with my old cs scar, nothing to do with the gd. They kept an eye on ds2s blood glucose for the first 24 hours but he was fine. Hospital policy seems to vary so I'd find out what yours is then you can work out what you'd be happy with and work from there.