I did sibling class for ODD when I was pregnant with DS and it was in mid December and DS was born the first week of February. I would do closer to due date.
We didn't do sibling class when i was pregnant With YDD because ODD already had been through it and DS was "too young" for the class. They say 3 and up. It turned out fine, he didn't miss a beat an is a great big brother. He loves babies though so that was a good thing
The only time you should look in your neighbor's bowl is to make sure that they have enough. You don't look in your neighbor's bowl to see if you have as much as them.