You will need Gibbed's Save editor:
http://social.biowar...index/9776690/1
Install to: C:\\Program Files (x86)\\Origin Games\\Mass Effect 3\\Binaries\\Win32 (This is for Windows 7, don't know about another OS, but it should be similar). Also check the readme if needed.
After that, make a new character, selecting the hairstyle you want. As soon as you have control of your character, save your game and quit.
Open the saveeditor, then select open, and find your new character and the save. Go to the raw tab, then under: squad - player - appearance - head morph, look for hair mesh and copy it. Open a new instance of the save editor without closing this one. In this new instance, open the character whose hair you wish to edit. Follow the same path to find the hair mesh, and replace.
You're not done however. Return to the first instance of Gibbed's and under head morph, look for texture parameters. Open this, and you will open a new mini window with several lines of coding. In the second instance of the program, also find the texture parameters tab and open it. From here, copy and paste lines 0 - 4 of the coding from instance 1 to instance 2, which will all be under the value label (ignore the name label). Close the first instance, and save a new game on the second instance, making sure that you're saving the new game to the correct career profile.
This should work. If it doesn't, please post again.