>>375206828
 how would i make the plane show the correct spot from the texture?

you'll have to learn uv editing to position each part of the mesh on the texture if you want to do it that way.

if you have the head already textured and know where it goes, you could instead just make copies of the head texture with different mouths via photoshop or whatever and make unique materials containing each one in unity, the animation can change those. It doesn't have to involve any blender work.