Open assets0.pk3 with winzip classic interface and find the two paths "models\players\_humanoid"
one file is humanoid.gla and the other is animations.cfg
Highlight the two and extract to base using folder names.
Then extract all the files of the skin you want to use in the same way (be it a downloaded model or one from assets0.pk3)
Run modview and click open, find the "models/players/playeryouwanttouse" model.glm and select it.
All should be well now.
thanks ill give it a try