I agree with the scarf joint because of stability. This is my first attempt at neckbuilding, I got past the scarf joint. If I can pull that off without a jointer, you most definately will too. Think about the satisfaction you're gonna have after the scarf joint.. awesome man, AWESOME!
C'MON - DO IT!
Edit:
Regarding the thin lam in the joint, don't feel like you have to do that now.. I'd lam the headstock instead, body being walnut it'll be sweet. That is, if I'm not mistaken bout the body being walnut.