A typical canine pregnancy is about 63 days. It could take three weeks to a month before you can feel anything in her belly but be carefull pushing. You can hurt the puppies.
The best thing to do is to have an x-ray taken. The vet can count the skulls/spines and tell you how many she is going to have and if they are going to be able to fit through the canal. The skulls won't show up until they are calcified so the x-ray needs to be taken at about 45 days after breeding.
Price really depends on the vet that you choose. This isn't an emergency so I would take the time to call around and find the best price. Even if you don't get the best vet, you still get to look at the x-ray and you can count them yourself!!
Hope this helps and good luck with the babies!