Going to the Italian Grand Prix at Monza

Hello everyone,
Greetings from Brazil :)

I’ll be at Switzerland next September and now I’m planning go to Monza GP. My first race in loco.

But, before dive deep in, I have some doubts:

1 – My plan is arrive at the circuit around 1PM. Is it too late or it’s a good time?

2 – I’m planning travel back to Switzerland around 6PM. Is it possible exit the circuit and take the train at this time?

3 – I read a lot about “general admission tickets”, but not sure if will be a good option. GA allow me to seat at any part, but I think the ideal is choose a grandstand where I can choose the seat, right?

Thank you so much!