No parts needed,TCW, they just do not wear out. ALL the 870s have totally interchangeable parts within gauge, up to the recent safety and dimples changes.
A suggestion, shoot it like it is for a while, get the stock and you in agreement,and then decide if it "needs" anything. A recoil pad,if there's not one on it, would be an exception.
And, start off with lighter loads. You may handle the barnburner loads fine, but the lighter kickers will let you concentrate more on form.
Enjoy,you've got a great new tool there...