Puppies, you are going to be WONDERFUL!!!!
My advice to you is read lots of great stories and inform yourself as to what's going to happen in your body. Having said that, nothing will adequately prepare you for what it actually *feels* like to give birth, because it is just so awesome, and such a privilege.
You are strong, capable and powerful.
Natalie's birth was really tough, and it went for a long while. But it was the most ecstatic experience of my entire life. I'm nervous about doing it again, sure. I think it is natural to feel aprehensive before such an amazing experience. But I know I can do it, and I know there is absolutely no feeling in this world like holding that precious baby to yourself after struggling to birth her - it makes your heart burst.