Personal Skin Model Hack or whatever you call it

Hello, so heres the request

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

http://filesmelt.com/dl/hlmv_2010-01-31_00-25-10-18.jpg

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: http://www.mediafire.com/?rzg4ng1xymm

Thanks in advance.