Has she passed a blob of really yucky looking stuff yet? That's the placenta. My cat only have 3 her first litter and we lost one of those. The bubbly breathing could be where the kitty has some amneonic (sp?) in it's nose and lungs. If you have one of those nasal thingies for babies that will suck it out.
Like someone said, leave momma to do her thing. Cats see to know better than any other critter I know how to give birth all on their own and take care of it all. She may actually up and move the kittens if too many hands are on them.