Don't change that light. It is lighter than the newer models. It only has a momentary switch, so it doesn't lock on, but thats ok. They are heavy with the newer SF light, extended mag, and full side saddle. I sold my HD 870s during the pandemic because of the weight.
Look at the lifter when you get it. It should have a u-shaped cut in it. That means it has the flexi-tab modification which which you want on a self defense shotgun. It allows you to clear a shell that jumps the shell stop by racking the pump. I bought an old wingmaster and had to replace those parts when I set it up for HD. Now I own a Benelli M2 instead.
You will like that gun. I set up my 870s just like that when I had them.