if the above link doesn't work, you can odin the NE2 firmare. I'm not sure you go to MC2 after being on 4.3 or above, even if it was AOSP. Here's Garywin's NE2 link: thread linky
and Samsung's official: page linky
. If you use either of them, it's a lot harder to restore back to MC2; Apparently Samsung did something with the recovery. Plus, you'll get Knox and you'll get the warranty void when you root; probably not a big deal since you've probably had the phone for over a year.