Depends on the doctors, as Michelle said. GD isn't scary: most people manage it with diet. Some do have to inject insulin and normal diabetes CAN result from GD, but that doesn't mean it will. GD doesn't mean you will have a big baby, just the chances are a bit higher.

I can't tell you what's going to happen because, right now, no-one knows. It depends on the severity of the GD and if you're borderline on the first test it doesn't sound like it will be too severe, so things should proceed as "normal" - or as normal as pregnancy is allowed to get by the doctors!