A gruppo can contain wheels and brakes but not necessarily so. Your gruppo is like saying I want Dura Ace - that is your gruppo; but you might pick different types of brakes for your hand size, or wheels (dura ace does make wheels but they are take a while to get usually); A gruppo does not "usually" contain wheels - Sometimes they include the headset, but not always.

I think you got it all with your post and the next, but there are all the little things, brake and shifting cables, little end caps for your cables (I forget what they call them), shifters if the brakes are separate from shifters; headset; handlebar tape; that's all I can think of now