Complex sentence: The original Duo Dock was replaced by the Duo Dock II, which added AAUI networking and compatibility with newer color-screen PowerBook Duos; a replacement lid was also available to allow use of these thicker color Duos with the original Duo Dock.
Split into simpler sentences: The original Duo Dock was replaced by the Duo Dock II, which added AAUI networking and compatibility with newer color-screen PowerBook Duos. A replacement lid was offered to allow use of the thicker color Duos with the original Duo Dock.