New headunit, newbie question

cossie1600

Guys, I know nothing about stereo and headunit on cars, I haven't upgraded one in 10 years. Bare with me, I have a couple questions.

I basically want bluetooth phone/stream on my base car. After driving my Lexus, it gets annoying to have to remove the phone from my pocket and hook it up through AUX every time. I figure if I am going to spend the money, might as well get a double din to get the DVD feature and possibly navigation. Here are my questions

#1 Is NAV on the modern head unit worth it?
#2 Do any of them have HDMI input for video?
#3 Since the car is so loud, can the bluetooth mic muffle enough noise to make the upgrade worth it?
#4 Do i need an amp?
#5 Anyway to keep steering control?
#6 Do they have Android system built into them?