If the S.N. on the stocks match the guns, I would not replace them, if they do not match then it's up to you. If the gun is to be a collector then put the nicest stocks on it you can find. Stocks that have the same S.N.'s are prefered. If the gun is going to be a shooter, if it were mine I would invest a few dollars and install a set of Houge or Pachmayers rubber grips so your diamond magnas don't get banged up. Model 15's and Diamond Magnas ain't made no more!! Model 15's or as they were known before model numbers as "Combat Masterpiece" are just about as nice, well balanced, accurate, rugged handgun as was ever made. Basicly a model 10 with adjustable sights; the model 10 is the offspring of the .38 Military & Police which got it's start in the late 1800's. Model numbers appeared in about 1957. Being a purist, dyed in the wool S&W Collector, if I had a pristine early engenieering change 15 with orginal stocks, it would not be an every day carry around bet and banged around gun. IMHO, they represent mechanical art work, a thing of beauty. If you want something to carry around get you a Ruger GP100 or an SP101. It's your gun. Just my two cents.
OH, if you want to take them off again, lossen the screw leaving just a couple of threads still holding and push on the screw, this will lossen the side with the eschion, don't pry, thats the quicest way to mess them up. Bach the crew on out and then push the other side off from by going thru the frame. Always, Always, Always use a well fitting screwdriver. If you get adventurous and want to start turning other screw, purchase hollow ground screw drivers of the correct size. Otherwise you will bugger up the screw heads. That makes me cry.