게 달라지다

become different, change noticeably

달라지다 is becoming different — built from 다르다 "be different" — and describes a change that happens rather than one you make. 크게 달라지다 "change much" fills four lines, and three of those are negative: 새해가 된다고 해서 크게 달라지는 건 없죠, "it's not as if anything really changes just because it's a new year". 이렇게 달라지네? is "wow, what a difference", said when something visibly shifts. For changing something yourself, the verb is 바꾸다.