Lionel had trouble matching the post war paint for their celebration series release back in the late nineties. There was an article in the local paper (FreePress) at the time they were doing this model and the Lionel rep was saying the original engines were painted with an automotive lacquer and that just wasn't possible any more. What they did finally settle on was pretty close match for the color but the finish was off. Original was a very high gloss, smooth finish. The PWCS unit was more of a textured satin. At normal viewing distances it was a good match, side by side not so great.
Unless the dings/nicks are really bad, I'd leave it alone. You could take the unit to a auto paint supply store and see if they can custom match it. This will be expensive because you have to buy the paint by the quart and then pay to have it loaded into a spray can or use an airbrush to apply it.
