GD veteran reporting in.
I've had GD with both of my pregnancies, firstly diagnosed at about 30ishwks with C, then a bit earlier with O. With C, my readings were quite high to start, so I was diet controlled for a few days but with the constant finger pricking, but as my readings couldn't be controlled with diet, I moved to insulin pretty quickly. Towards the end of my pregnancy with C, I was injecting novorapid x3 a day (and additionally when my readings went high after meals) and then the long lasting insulin (can't remember the name) at night. I was on a strict diet the whole time too. With O, it was pretty much the same, except I managed to get away without injecting insulin at lunchtime, randomly. Again, I was on a strict diet the whole time. I found breakfasts especially hard to manage, my readings were always highest then. The diet was hard and boring, but at the end of my pregnancies, I was the same weight as when I got pregnant, and actually had lost a dress size once I'd had the baby! Sadly I've put it all on again now 
It impacted on my labours both times - I wasn't going to be allowed to go overdue, I wasn't allowed a water birth either as I was told I would need constant monitoring whilst in labour. As it happens, I laboured spontaneously both times so didn't need to be induced. I was very philosophical about it all, I'd rather have my baby here safely by whatever means necessary rather than get het up about the fact I couldn't do it in water.
I was seen by the consultant every month at least, the diabetes midwife between, and also the diabetes CNS' regularly. First time I was regularly on the phone to a dietician too, she really helped me with what would work to keep my sugars down and what wouldn't. Second time I didn't need her help as much as it all came flooding back as it hadn't been that long since I'd needed her.
HTH a bit, happy to answer any more questions. Workinghard also had GD, rusty was told she had too (although towards the end there was a query as to whether she did actually have it) so there are a few of us x