A few questions: How much fresh ginger should I sub for the ground? I'm out of granulated sugar (it does happen), can I sub brown sugar, will I be...

Thanks!

I'm not Merrill, nor have I made this recipe, but I've made several million cookies in my life... I don't think fresh ginger is an acceptable substitute for ground ginger in this recipe. They are two completely different products. Different flavors, different textures, not at all the same thing. Second: you can always sub brown sugar for white, but remember you will be creating a completely different cookie. Brown sugar is loaded with molasses, and gives a very different flavor. As well, it has a fairly high moisture content compared with granulated sugar, so you may need to adjust the liquid in the recipe.
I always recommend a baker follow the recipe exactly the first time, before trying to adapt. Otherwise you have no idea what the creator of the recipe intended the finished product to taste like.