Wondering how to take off the original take down screw on the 88 and replace it.
No, BUT, it will keep the screw captive so you don't lose it or drop it in the mud or down a drain... I don't know if a hardware store will have that exact clip but they may have a circlip ("e"-clip) that will work...so i take it i definitely need it
I would wait until you have your new Maverick in your hands and see what they sent you. I've seen them send a small brown envelope with a couple swivel screws in it. Maybe you'll get lucky. Some barrel screws are threaded ,,,,, some aren't.
That is the correct part number.12030.
Keep us posted on what they sent you and how the new Maverick came.