[Coda]

The magnitude probably means the magnitude of the vector at that point in the field.

I think the only information you wouldn't be using is the position. You need the charge and the mass and the orientation of the field. And I think that the position is meant to be a red herring -- part of the problem is to identify that you DON'T need it because it's a UNIFORM field (you WOULD need it if it were a point source directly above the object, due to the inverse square law).

That said, I actually don't understand why they gave two different positions, unless it's trying to suggest that it fell some distance before finding equilibrium, but that... doesn't make sense if the field is truly uniform.

EDIT: Oh, it should be noted. The magnitude of the electric field is NOT the force it applies. It's measured in newtons per coulomb.