Is it possible to customize a genesis/dynamlk WP site's navigation to include a horizontal drop down instead of a normal drop down?

I hope I worded this right, was curious if a nav menu like this http://ift.tt/1uAm3uG was possible or one that hovered horizontally versus a drop down? I am new to WP dev and everything ive read so far says to change the code in the header.php file. Is there a way to do this without modifying the header? How would one go about coding this?