You can do it! After the NB stage it just gets easier and easier.
I was like you before I began CDing. I had done all kinds of research and was set on CDing. Then when the time came I was just too chicken to start. Only when DS was 3 months did I go ahead and tried them. Now I regret I did not start earlier... all the cute dipes I could have bought with the money I spent on sposies for 3 month...
It is unusual that your baby will soak through a prefold before the time you would usually need to change a sposie. But if you think it still is a lot, you can always add some extra material in the middle of the diaper like one of the PPs suggested (a wash cloth or a doubler). We find that hemp makes wonderful doublers.
For overnight, get a good thirsty doubler with fleece topping. You can buy them ready or you can cut pieces of micro fleece yourself and lay on top of the doubler. This will wick the moisture away from your baby and keep her dry all night!!!
Later on when your baby is not soiling the diapers so often, you can move on to pocket diapers. We use them at night and when we go out. They are trim, easy and hold the baby dry
Edited to add - I have to second the PP:
Get rid of the sposies you have left ! It is much easier to do it cold turkey.
And yes, do hang around here! It is the best thing to keep you hooked on CD. The only problem is that you might get addicted :LOL