facial animation: we almost exclusively use bones in the face for animation these days for our game animation. Usually the mouth is just a sucked in umm... area... think of punching a big slab of dough and having it close in around your wrist. The surface is still in tact, so no cutting. Then the teeth and tongue are added geometry either constrained or parented to the jaw bone or root of the neck. The end of the chain, the effector, is weighted to the verts on the face, so they each have a range of influence. I'll have to see if i can dig up an old model to send you. What version of Maya are you running?

As for face modeling, most of the folks i've seen around here use the half sphere mirroring technique. I wish i knew more about it so i could give you some complete instructions. I've yet to see a good tutorial that shows what is actually used in production. I'll see what i can dig up...