Newbie: HDD nav/HUD - Replace Nav/Entune? Mac user.

Hi All, I'm a newbie, just purchased a 2013 Prius Hatchback Five yesterday. It has over 86,000 miles, but well taken care of. As it hopefully has years left, we are considering replacing the head unit, as the Nav/Entune seem to be so reviled. We also like the idea of a larger screen, versus the small screens of our phones for navigation.

I had a few questions - also, while I am fairly intuitive/great with tech/a Mac, and good with my hands, I have little electronics experience and am poor at Windows. I am very visual and follow directions well, and advice is appreciated.

1) If we change the head unit, will the HUD still work? (with arrows projected onto the front window showing the MPH/map turns/efficiency of the engine);

2) Will the "touch tracer" still work?

3) Will the Safety Connect still work? (No idea if it is connected)

3) I would like to customize a new HDD, but use a MAC computer. Are there recommended replacement head units which interface/can be customized with a MAC?

4) The Five comes with the HDD head unit. The map is from 2012. We don't really need the apps. If the HUD arrows only work with the OEM system, we may just use it as it, and bring our Garmin with us on trips for local roads as backup. If we do this, is it worth updating the maps at least one time?

5) Is there any good/bad reason to download Entune? The Toyota literature talks about more efficient navigation. Is this true for the HDD unit? The Apple Store reviews talk about it being a problem. Also, does Entune eat data? Is it easy to turn on and off on an Apple iPhone?

I have an Apple iPhone 5s with the most recent iOS update installed.

If Toyota only had customers pay a fee based upon hardware configuration, then had customizable elements available on their website for download, where each individual could just "drag and drop" customizable elements such as maps and apps onto an iPad/desktop (even have have a kiosk available to "try out" at dealers), then transfer them onto a USB, (or better yet, a phone) for seamless car updates. Everyone wants to customize now - Toyota would attract a whole new audience with features such as this. If I didn't need/want the HUD I would just stick an iPad on top of the current Nav.

Thank you for any and all advice!!!