For the smile (and eyes) I got a picture of a LEGO face into Blender and used it as a reference. After that, I created a plane, extruded it several times and worked with it until it resembled the smile. Then I subserfed it once (twice for rendering).
Applying the face to the head, I created a Bezier Circle and and parented the smile and eyes to it (Mesh Deform). So the face isn't actually on the head at all. I'm sure there are easier/better ways of doing it; however, this way seems to work for me.
And actually, BG, I am using the LDraw parts, or at least, I am now. They are nice for getting the proportions right, but the actual meshes are a nightmare, so I've had to heavily modify them. The reason I switched was because I wasn't getting anywhere doing it from scratch, and my main reason for making this model is so I can animate it, not just to have made a model. However, I am very happy with what I've accomplished.
"[It] was the theme song for the movie 2010 first contact." ~ A YouTuber on
Also Sprach ZarathustraCGI LEGO! Updated occasionally...