for the minimal cost of a damper after overhaul it's a good idea.
You can visually check yours for leaks around the outer edge of the front face and the text book method for checking is to use sandpaper/emery paper to clean off the paint at 4 points
3,6,9 & 12 o'clock & then measure the thickness of the damper at those 4 points.
A variation of 0.010" in thickness is all thats allowed...any more than ten thou and the fluid inside the damper has gone off and the damper is u/s.
If you're going to buy a new one get the 400hp damper....p/n 217323....slightly larger than the standard 211915 damper but does a better job.