This is something you should have researched and prepared for BEFORE breeding your girl. But at this point, I'm sure you realize that, soo...moving right along....
Start with this site:
www.debbiejensen.com
It is loaded with information that will help you.
How big is your girl? What about the dogs that run in her line? What about the male she was bred to? How big was he and the dog that ran in his line? These will be very important factors to help you determine if she will be able to deliver naturally or if you will need to heavily consider the possibility of a c-section.
Set up an appointment w/ your vet around day 50 of her pergnancy for an xray--this will give a good esitmate of the number of pups and will indicate to your vet if any of them appear to large for her to deliver naturally.
Try your best to find a well seasoned breeder in your area that would be wiling to assist you during the whelp. (Even if you have to pay one!) A good place to start would be with the breeder you got your girl from? Maybe you could ask your vet to recommend one?
Good luck!