Good technique to superimpose face into moving character in AfterEffects? I'm going to direct a music video for my band (I have experience in film production, direction and some video post-production) and I want to achieve the following effect:

Film the singer at a high FPS (with a phantom hd gold) and then slow it down substantially. Then, at the same location, film the singer actually singing the song, and then in post production superimposing his face (without it being slowed down) on his own body from the previous shot.
Final effect: his body and background will be moving in super slow motion but he will be singing the song at normal speed.

I'd prefer to do it in after effects since it's the software I have most experience with.

I know sometimes a similar effect is achieved by speeding up the song and the singer lip syncing to that, but in this case it would be impossible because I want film at around 1000fps and slow that down, so it would be too fast.

I wont move the camera and I know I have to take in account shadows and lighting in both takes so they match.

Any suggestions?
There is some substantial work that would go in an effect like that.

You'd have to first track the face of the slowed-down singer in 3D-space and apply a mesh to it, which sticks perfectly to his features.
Then, you'd want to rotoscope the normal-speed singer's face (which is going to take a lot of time alone) to then apply that pass with your tracked transform to the slowed-down background. You'd also have to match the change in shape of the head, such as when opening the jaw. This is not only applying to the face, but the whole head really.

(If I understand your vision correctly,) this is a high-end job that would take a few weeks for a professional compositor.

I would recommend you film the entire background in slow-motion, then shoot the singer in front of a green-screen so you don't have to rotoscope him out of the background. You can then simply key your singer in normal speed, track your slowed-down background (if there's movement in the camera) and place your singer on your background, applying the motion of the camera.
This method is not a walk in the park, but significantly easier than the approach above.

Hope I could help, have a great day :)