Another way to change the appearance of your character that is fairly easy - it just takes
three four easy steps!
Step 1: Make sure you have the PC version.
Step 2: Create your character. When you are satisfied with the face and how it appears, do a full save - BEFORE EXITING THE SEWERS (or whatever chargen mod you're playing). Make sure you still have access to the CharGen Face Editor. Exit the game and rename the file to something useful, like, "*charcter_name*Master". This will be your master face file. DO NOT SAVE OVER IT.
Step 3: When you want to change your character's appearance, open the "master" file and edit the face to add age, change hair color, length, whatever. Save it under a new name.
Step 4: Download http://www.tesnexus.com/downloads/file.php?id=7808. Load the "revised" face save and copy the face. Then just paste it onto your latest game save.
Step 4 takes like ten seconds. The key is making sure you save your game while you have access to the CharGen face generator. You can use the console, too, but I like to work on my face, then see how it looks in game, even while I'm changing it, without opening the console again and again. Also, I find I get better faces, but maybe that's just me.
~ Dani ~

Edit: My characters modify their appearance over time, depending on role play. One character, a prisoner upon arrival, had a rat's nest for hair and wore no make-up. By the time she had 100k in the bank, that rats nest was a finely tailored hairstyle and she sported eye-shadow and lip color. Since it's so easy to change hairstyles, I do that pretty often.
I don't think you can add scars without editing the face texture file. I have thought about broken noses, if I could figure out how to edit that in the Face Generator.
~ D ~