Hey Girl.
I would Xray her so you can see the size of the pups heads and how many pups you are expecting.
Check this site out
Canine Reproduction Video and Book on Breeding and Whelping dogs by Debbie Jensen for dog breeders and Whelping Supplies needed to deliver puppies.
It has a lot of info, there are also more helpful sites but I think this one would be good for you. Email me, I am going to take a shower now but will be back on in a bit.