hahaha.. "맘에 들어요" "좋아해요" are same meaning. Yes, you are right. "맘" is a heart, "들어요" means listening to. but " 들어요 " has another meaning. it means " like " so, " 맘에 들어요 " means i like it.

From what i have learned 맘에 들어 or 마음에 들어 is usually used when showing appreciation for something for the first time. It translates into "(something) enters (my) heart". 들다 means a lot of things but one of them is "to enter". So it's an idiom. But haven't done much research on this expression at all i'm afraid. I just heard it being talked about in a lesson a while ago so i'm not sure when it's appropriate to use it instead of 좋아하다.