For this guide you will need the TES Construction Set and Wrye Bash.
First of all, you will need a blank Plugin (.esp). There's two way to get one. The long way is to open the Construction set, go to file > Data and load Oblivion.esm. When loaded, go to File > Save, give it a name and save.
The Fast and lazy way is to go in Oblivion\Mopy\Extras\ and copy the available blank.esp into you data folder and rename it to what you want. I named mine _Faces.esp because I find it easier to find that way.
Now to import your face into it, Open Wrye Bash. In the Mods page, locate your blank plugin, right click on it and chose Import > Face.
You will now have to browse to the save file containing the character you want to import. When done, a small information popup will tell you it create an NPC with the name sgUnkaYourName.
Your character Face is now in a plugin and you can do modification to it in the CS. If you character use a non vanilla race, you will need to load the mod that have your race along with the plugin that have your face. Open the CS and go to file > Data and double click the race mod. Now locate your face mod and double click it, click the Set as Active File button at the bottom and click ok to load it. (NOTE: If you don't want to modify the face but want to add it to a follower, load your follower mod and set it to active instead of your face. Read the instruction of your follower mod to know which file to load.)
In the Object window, go to Actor > NPC. A list of all NPC will appear on the right, including your. Click S to go down to the S faster and scroll down to your NPC sgUnkaWhatever. Double click you it and select your character race in the Race drop down menu on the left. Put a check mark on Head on the right. This is important if you don't want to make the CS crash.
On The top, use the small arrow until you can see the tab Face Advanced. This is where you can modify your face. You have the same option than in the game but with more control. You can also use Asymmetry, if you want to. You can move parts of the face directly with the right click in the small render window. The Best part is if you mess up, you can CTRL-Z to undo!
There's a Copy and Paste button so you can either copy it or paste in another face directly. (NOTE: If you loaded a follower along with your face, Click the copy on your face, Locate the follower NPC in the Object Window and double click it. Change its race and put a check mark on the Head then go to Face Advanced, and Paste).
Click OK at the bottom of this window and File > Save.
When you are done Close the CS. If you modified a Follower, don't forget to re-arrange your load order. If you have only done some modifications on the face, You probably want your face back in a save file. I strongly suggest that you make a back up of your save first. When done, open Wrye Bash and go to the Saves tab. Right click on your save and select Import Face...
Now it will automatically open a windows in you save folder so browse back to your Oblivion data and select the esp with your face. A small window will open. Click the npc name on the left and don't mind the check boxes, they are not needed for this. Now click Import and you will get a message "Face imported". And this is it. You can now load your game to see your new character.
Note though that sometime when you do heavy modification such as trying to bring the mouth higher than the eyes, your character wont look the same in game. Remember to save your esp often and make backup if you do a lot of modification.
