to install these skins, replace your original materials folder with the one provided 
it can be found here

 C:\Program Files\Steam\steamapps\username\day of defeat source\dod

to uninstall go back to C:\Program Files\Steam\steamapps\username\day of defeat source\dod
and remove the player folder, no worries the game will automaticly replace the missing files with default ones!

credits:thank valve for the models

Author: T/5 Cole [9th ID] S-4 S1    A.K.A. - barcon