how to upgrade from 10.6.3 to 10.6.6?

I JUST bought and upgraded to Snow Leopard 10.6.3 a week ago, the minimum version I needed to be compatible with my new Microsoft Word 365 2011. Then I just realized I want the latest Pages, which is only compatible with 10.6.6 or later. What are my options? Do I have to buy a new upgrade or is it free to upgrade to 10.6.6 since it's still Snow Leopard and I did pay for Snow Leopard?

Also, how would I know if my old 2009 Macbook Pro 5,5 is compatible with 10.6.6?

Thank you!