Guide on adding a new model, animation, and creature to HoMMV

In principle, is this possible? I mean, can you extract the model and animation files?

In principle, it is possible – if I remember correctly, you can use ARCHANGEL to extract the model and skeleton that are not linked (you will then need to do the model skinning), and using a plugin for 3DS Max 2008, you can load the skeleton and animation.
You can also load the model into 3ds Max after pre-processing the model file from the game using the mesh2wrl_by_CrazyPill program (without the skeleton).