Assuming the pages are completed, you only need a drop-down menu with columns that, when selected, take you to the pages your website already currently has. This is a rather simple task and can be completed in a few hours.
If you are looking for fluidity regarding animations, transitions, and styling, CSS would be a more preferred language. But if you are looking for dynamic alterations of data and elements of the GUI then I agree that Javascript is the best approach.
Either way, this isn't too difficult of a task and can be completed in a few hours.