Personal Skin Model Hack or whatever you call it

Hello, so heres the request

I currently have a personal skin, which looks like this:

I would like the head of my model put in place of Nick’s head from Left 4 Dead 2, along with a pair of glasses attached to the head (Kleiner’s, maybe?). I do not need any skinning done, I will do that myself once the model is complete.
Download link for model:

Thanks in advance.