How to import a 3D head model with moving eyes/mouth

Hi. The best way of doing it depends on how complex your mesh is. If it is as simple as the one in the video, you just assign different parts to corresponding bones
If it is more complex, then i think the best way is:
- clone a head, export, open, rename to Reference, delete the mouth cavity;
- import or append your custom head;
- select the reference and symmetrize it;
- using proportional editing, try to ( roughly )mold the maxis head to the custom one ( so that lids match lids, nose matches nose, etc);
- try transferring weights, uv_1 and vertex paint from the reference to the custom one and checking how it works in-game;
- if unhappy, you can add Shrinkwrap to the reference, project it on the surface of the custom head, then use sculpting tools to move things around. After that, retransfer data.