I did a ‘sort of’ John Locke as my second head, check this link:
I think you have got some likeness in there, but maybe you’ve sub-divided a little early.
It’s a good idea to get the basic head shape right (which I think you’re close to), then sub-divide, and add details, going from lowest to highest sub-division only when you’re happy with what you’ve got so far.
For texturing, check out the artists in action series, especially work from this man:
If the vids don’t work, try downloading the latest version of quicktime, as that should cure that problem.
Also, try this script out in zbrush:
(I would like to give credit to the person who put that zscript together, but I can’t remember who it was)
That should give you a bit of inspiration too.
Good luck, I hope all that helps,