When I first got my 3DS XL, I thought my top screen was a tiny bit wobbly too and I got mine new. It's not too wobbly were my screen would constantly move while playing but I do notice it when I open/shut my 3DS.
I don't get what you get with your charger though. Are you using the official one?
I don't get what you get with your charger though. Are you using the official one?