Some words about the model:
The model contains many-many polygons, blah-blah-blah-blah... No LOD models. The model uses the head of Barney from the original model.
Extract the zip file into your "STEAM\steamapps\<...>\half-life 2\hl2\" folder or your mod's folder. (if ask, overwrite the old materials)
I hope you'll like this model,
Next mission (if it's possible) to change the Super Combine Soldiers with the Snowtroopers models.