I think Napoli will have a very difficult time in this match, with Milan having been in very good form lately, all the teams, even the strong ones, are afraid, then Allegri can't wait to measure his team against a very high level team like Napoli, it will certainly be a good match.
I will put my money on Napoli to win, if I must, in that game. AC Milan is in top form now, but I don't think they will be able to beat Napoli. Most teams have not really faced a tough opponent, but Napoli performs better against tough opponents. Milan is inconsistent, and that might play against them this weekend.
AC Milan has an advantage of not playing in Europe, so they don't need to reserve any players. Plus, they will be playing at home, so they can use that to their advantage, but still, I'll bet on Napoli.
If you want to play it safe, I think an under 3.5 goals will not be a bad option. Neither teams concede much. They might not want to attack too much, so the opponent doesn't exploit their defence. I've not checked it to see the odds, but if it's reasonable, I'll bet on it.