[ReQuestion] Race swap

[thesixth]

Hi everyone!
I am working on a little modification wich includes retexturing, and two small model swaps.

I've been trying to swap from Dranei (both male and female) into Undead and I end up with a problem with the Jaws of the undead model.
The female model works fine, but on the male model, the chins are missing!
It only appear correct in three of eight (i think) facial variations.
I have searched the forum for a sollution to this and I found one, single guide which didn't work for me, or I didn't understand.

Eitherway, I have a similar problem with a race swap from Tauren (again, both female and male) to Human, where (atleast on the male model) the facial hair appears to be transparent in some wierd way.
I can actually se right thrugh his face, plus the hair appear as green as could be!!

Can anyone tell me how to solve theese issues or does anyone of you have a file to upload for me ?

Thank you for reading this!

Ps! I know I have that lame-ass leecher status, but I intend contribute my work (once I get it to work)...