치마입고 가려고 하세요? = 치마입고 가려고요? (Do you want to go out in the skirt?) "~고요" is a short form of "~하려고 하세요?". do you want to do(~something)? Usually we say like this under an unusual situation. It sounds like that it not normal thing. 치마입고 가려고요? it means, I don't think it's good idea that you go our in wearing a skirt. (for example, you go out running now and I think it's so weird that you wear a skirt)

In this case, I think you should know what is "려고요." 가다(go)+ 려고요(would like to)=>가려고요 자다(sleep)+ 려고요(would like to)=>자려고요 By the way, 려고요 ≒려고 해요, and the colloquial[slang] expression of 려고요 is 려구요.