Unless you have a decal laying on top of the finish, which is not likely, you won't be able to remove the decal without ruining the finish on the headstock. If you do remove the decal, chances are that there will be an outline or a complete impression of where the decal used to be because the decal has hidden the wood from light(sunlight, flourescent or incandescant) and that area will be lighter than the area where the decal wasn't. The laquer or the wood has begun to darken and the decal area hasn't. I see it all the time when I strip finishes from guitars.
Peace
Pat Wilkins
Wilkins Guitar Finishes
www.wilkinsguitars.com