Here are a couple of links that should get you started for face replacement and lip synching:
These types of effects start with Production Planning. Things you'll need.
- A bunch of shots from the same angle with mouth shapes for the common vowel and consonant sounds that you composite to the face
- Long steady shots of the face from the same angle with sufficient expressions to use as a starting point
- Some motion tracking software (AE's Mocha would do the trick)
- Shots from all sides of the head of the person you wish to animate
- A good 3D app and some modeling skills
- Skin, eye, and hair texture maps for the 3D model
- A good background plate possibly including the actor who's head you're going to replace with the 3D model
- Some motion tracking software
- A nice long shot of your actor (baby)
- AE's corner Pin plug-in (included)
- Some good matte and masking skills to separate the mouth, eyes and jaw from the rest of the image
There's no easy one plug-in or one click solution to this project. Any solution would require multiple layers, masking, and motion tracking or keyframe by hand work. Success depends on how well you plan the shot so that you have sufficient resources to pull off the effect.