Been there done that! :)
I was diagnosed with GD after failing the 3 hr test (take a snack for afterwards btw you'll need it). I was so angry and in denial about it which I found out is a very common response. My ob had me go to a diabetes center near Baylor for weekly or bi-weekly consultations. They prescribed me a glucometer and pee sticks to measure ketones every morning. I'd go in and they'd weigh me, look at my blood sugar levels, ketones and diet that I had written down for that period. Then I'd meet with other pg moms to discuss stuff.
The thing about GD is that, compared to a lot of other problems you can get while pregnant, it's fairly controllable -- either through diet and/or insulin. In the scheme of things, it's a pain to measure and record your food and blood sugar levels but it's not like preeclampsia or other complications. But if you do not watch your sugars or go untreated, you and your baby can end up with a whole lot of heartache.
My son ended up being born via c-section. I had to have an induction at 38 weeks because I caught a cold a few weeks prior and my blood sugar levels went out of whack (who knew cold medicine affected blood sugar?? Well I do now!!). The diabetes center said I needed to go on insulin. My ob (who I totally trusted) said it would take weeks to get insulin adjusted and that I just needed to have the baby. She wanted to wait until 38 weeks because we a) knew he was a boy and they take longer to bake and b) diabetic kids' lungs mature a bit slower.
Inductions and GD put you at a greater risk for a c-section btw but I still did my Bradley childbirth classes, got my doula and hoped for the best. Oh well.... When my son was born, my Dr had warned me that he would need to be monitored anywhere from a couple of hours to 24 hours in the nursery or nicu to make sure his blood sugar levels were ok (they were). I got to hold him a few hours later and he was healthy as a horse. Yes, he was big -- 8 lbs 6 oz -- but that also runs in my family so I don't know if it was the diabetes or not.
I can't stress enough how important it is to adopt a healthy diet and to educate your self if you do get GD. I think that was the biggest change it had on me. I've never been overweight but I did gain over 70 lbs when I had my son (breastfeeding rocks for weight loss btw). There is a slightly higher risk that I could get diabetes or if I were to get pregnant again I could very likely have GD again. It's a lot of record taking and finger pricking (which really wasn't bad), but somehow I managed to eat some chocolate every day so it wasn't complete torture.
Whatever happens tomorrow, I'm sure you'll do fine as long as you have competent a medical team on your side. good luck!