Firstly
Welcome.
I can't contribute as far as answering your long term questions. I can tell you that my '08 4.8i was pretty much trouble free but I lease so I'm out before the warranty is up and had pretty low miles when I turned her in.
As far as fuel consumption - I got 13.6 for mixed city/highway. My daily grind is NJ/NY rush. It depends how and where you drive. I bet you can tell how I drive
Good luck - it's a great vehicle.