Easiest way to customize this theme

A client started redesigning their site in WordPress using the Customizr theme. The needed help executing their vision beyond what is currently available in the theme.

Now, I’m not new to WordPress. I usually design the sites and convert them to WordPress pretty easily. But this is my first time working with the Customizr theme. I’ve done some research a bit and I’ve gotten mixed reviews on actually how easy it is to make changes to.

Here is the homepage design that they want. It isn’t too far from the original design of the theme:

Homepage Design

I’m not overly concerned with editing the CSS. I think the part I am struggling with the most is the header. The navigation is different than what is currently available. Is it as simple as just adding code to the header?

FYI – we are using the PRO version, with a child theme.