I just went through all this stuff a few months ago. Where I live though you can't start driving until after you start the in-car training, so you'll have an advantage, having already been driving!
Like Veggiejanie said, just relax and you'll do fine. I was terrified the first time I started the training but it wasn't nearly as bad as I thought it would be. When I did it, I just drove around and the instructer would tell me to do things such as pull into a parking lot and park, back up, etc. Mostly it was just about practicing turning corners, coming to smooth stops at lights and other simple things.
For the driving test to get your license, it's not much different. Just make sure you know the hand signals (left, right and stop), and where the lights, wipers, emergency brakes and emergency flashers are because the instructer might ask you to show them where they are (they did for me).
I had all the same bad thoughts in my head about how I was going to get too nervous, mess up and fail. But it ended up being a lot better then I had imagined. So don't worry about it, you'll do fine!