If you want it to look like stainless, go with Electroless nickel. I've done the plating for years in another life and the finish will only be as good as the prep work. Also, depending on the plating, you may throw components out of spec as a good nickel finish can be as thick as 5 mils. The NP3 adds teflon to the mix and that will also increase part thicknesses. Prior to any refinishing, get good solid pictures of any engraving such as roll marks, barrel markings and the Serial number in case they need to be re-etched into the finish. Check with the Feds in regards to remarking the serial number as I don't know the laws governing that.