so i guess you want to hange the used texture, not an advice on how to extract skins and edit them in photoshop?
well, basically you open magos and the unit and then go to "Windos -> Texture Manager".
Right-click on an empty space and choose import (you need to have exported the new skin from the .mpq beforehand) and choose the texture...
Afterwards open the Material Manager (in the windows tab too)
Now you need to find the right texture and double klick on it and press edit on the screen...
Now on the upper right hand side you can choose the new texture!
