For the front of the guitar (where the keys go -- I'm not perfect at vocabulary :p) I would convert to polygons, subdivide until I had holes over the proper proportions, delete faces over the holes, use the vertices to Create Polygon, clean up the rest of the faces using delete face/create polygon, then smooth as desired (then clean up w/ delete face/create polygon again, then polySoftEdge, etc.)

Make sure to combine then Merge Vertex after CreatePoly. There an easier way? Most likely... I don't know it though.