Change "add to cart" functionality on thumbnails page

On the products thumbnails page, I need to change the “add to cart” functionality; in most cases, the customers will need to select a quantity, and they get advice for how many they will need on the single product page.

How can I change “add to cart” on thumbnails to read as “order now” and have the click redirect to the single product page rather than adding to cart?

http://wordpress.org/plugins/woocommerce/