two questions about events

hello, i am trying to attend the rally on the 18th in buffalo, i have a couple of questions:

1. I heard that the tickets will become available for the event on the 15th (please correct me if i'm wrong). does this mean that I will be able to get one at midnight of the 15th, or do they drop sometime throughout the day?

2. does a ticket assure me entrance? or will I have to end up waiting on a long line hoping to get in? the weather is still really shitty and people who went to the sanders rally had to wait like upwards of 3 hours outside in the rain to get in, and i'm already pretty sick, so I don't think I'll be able to