If you have a CAD model of the shape,its an easy job.If not,you will get what the person making assumptions about an approximation gives you.Would I be right in guessing that you lack experience with CAD and CNC?If so it makes it really difficult to convey any accurate idea of what you require.Would you be looking for a template for the inlay as well as one for a slightly larger recess in the guitar body to sit it in?