GECK NPC editing help

[nexiliator]

First of all, i just want to say that I am a complete noob at all of this GECK stuff. I downloaded it a couple of days ago, and I have been VERY slowly learning how to use it, through Bethesda's tutorials and some youtube videos, but I really am having trouble with editing an NPC. To be more specific, I downloaded a race mod that adds the new race as a preset you can select, and I was trying to apply the preset to a few different NPC's faces, but it the face either won't change, will change to something completely different, or the face will change and the hair, eyes, and mouth will be in place but the rest of the head and face will be waaaaaaaaay above the hair and everything else, and when I load the game with the last problem's esp active and say I tried to edit Cass and I would go to the Mojave Outpost to see if it worked the game would immediately crash. Is this something I'm doing wrong? Any help would be appreciated.