I received e-mail notices for my dogs. The notices say "entry processed" pending final acceptance. However, I remember in years prior, when we used to have to mail them, you would get the same thing in the mail and it really means they're in if you get this.
What tickets to buy are up to you. If you plan on staying all the way through Group judging and Best In Show, you may want to get your tickets in advance for better seating. But, most of the seating during the day is sit where you want. Most people want to be seated close by the ring of the breed they wish to see (in our case, labs). The general admission tickets are cheaper, but the seating for the evening events is way far up.
