They are certainly not bolt on items. The 767 APB winglets also require the retrofit of massive reinforcement straps inside most of the length of the wing to support the extra weight and forces generated by their addition.
Fuel saving in order of 5-6%. Saving comes from less fuel needed for trip due to drag reduction, and less fuel needed for carrying the additional fuel not now needing to be burnt - and all despite carrying an additional 1-1.5T of winglet around.