3D Shading/coloring Help

[NinJato]

I have reached the limit of my skills.
I need this Fiona sprite 3D shaded. Right now it looks too much like a cartoon.
It is for the bottom right corner of a Metal Slug wallpaper I'm making.

The shadow is only a suggestion.
Please keep the pallet small (I'm thinkin' 3-4 shades per color).
A standard shadowing like a Street Fighter Character is also acceptable.

I'll do anything I can in return.
Please help

P.S. I found the original art in a Google Images search for "metal slug concept art".