Fernando hasn't changed much. He still is the somewhat shy guy he always was and he still says what he thinks - pretty straightforward. That has not always sounded nice and maybe made him look arrogant, something he is absolutely not.
The only things that have changed are that he is somewhat older now, and the most important is that he is now part of a team he really feels at home with. That feeling comfortable is very important to him - without it he does not function at his best as a driver and as a human being.
This is also one of the main reasons he decided that Ferrari is his last F1 team. It just does not get better anywhere for him.
I think he will always stay connected to Ferrari emotionally, even years after his retirement.