You can opt for monthly payments at the ticket booth. You have to put a minimum of 1 day's admission down if it's not a renewal, with the rest coming in monthly payments. The first monthly payment will be within a few days, in addition to the money you put down.
If you are buying a new pass online, you can activate it on a blockout day and go in. If you are renewing an existing pass, the expiration date is the same, just one year forward. I'm not sure if you can renew at the ticket booth and still get in on a blockout day. You for sure can't if you renew online.