"Do you have a moment?"
I think it's okay, but "chwilę" seems much more natural in such a context. The disproportion between Google search results of exact phrases "masz chwilę" and "masz moment" is suprisingly big: 60:1 for "chwilę". And a lot of results for "masz moment" are connected with physics...
It doesn't. It means "Do you have a moment, gentlemen?" - and in English you usually just say 'you' to everyone, so 'gentlemen' doesn't have to be in the English translation.
I removed it from the starred answers, as generally this course doesn't teach Formal You too thoroughly.