It will ask you if you have NAV or not - if you do there's a "Contact Us" button that tells you this when clicked:
The Performance Upgrade was mailed to owners on March 8, 2012. If you have not received the upgrade, contact us:
Hours of Operation: Monday – Saturday
8:30 AM -10:00 PM ET
Sunday 11:30 AM -10:00 PM ET
So apparently they mailed them today!
Or you can say No and download the update.