What are my options to recreate the box at the top of iTunes in Cocoa, or like Apple uses in XCode 4?
I'd write a custom NSView. Draw the background and border yourself in drawRect:. You can use NSGradient to draw the filled background, or alternatively you could save it as an image and draw that. You could probably use a white NSShadow to get the embossed effect for the border.
Finally, to get your text on there, you could just add text fields as subviews of your new custom view.