[greco]

Plan was to get a thin maple dowel and some glue and tap it in, sand the headstock down (putting a partscaster decal on) and clearcoat it.

You might find that the end grain of the dowel soaks up more clear coat and will look darker. Wait for others to comment/confirm.

 

[greco]

I guess fill in the hole, but not level to the top, then very carefully with an xacto cut a small circle/plug for the top and try to match the grain?

That sounds like a good plan. Trying to match the grain (apart from the obvious direction) might be a challenging task.

Good Luck with it!