Colts are made to be fired. Shoot it. Clean it well afterwards. In fact, since it still has stiff grease, remove the stocks and clean it well before shooting, to remove the grease. If there is a lot of grease, you may need to soak the revolver (with stocks removed) in mineral oil or kerosene, brushing gently from time to time, to remove all the grease. My favorite gun cleaning product is Eezox (but not for heavy grease), followed by a coat or three of Renaissance Wax. Do a search to find many threads here on these fine gun care products.Specially if you do not have the original box or the original stocks, I doubt a bit of shooting will affect the revolver's value. Lots of shooting will be lots of fun, and will leave wear on the revolver that will reduce the value. If you holster the revolver, there may be telltale wear marks left on the revolver by the holster, and that will certainly reduce the value.