Liferay ships with a pretty old copy of Vaadin 6, but most documentation and examples out now are for Vaadin 7.  It's pretty easy to upgrade the shared Vaadin environment to Vaadin 7, as simple as installing the Vaadin 7 Control Panel from the Marketplace.

When the Vaadin 7 Control Panel is installed, it will purge Vaadin 6 from the Liferay environment and copy an initial Vaadin 7.2.7 into the Liferay environment.

From there, you can use the Vaadin 7 Control Panel to upgrade/downgrade to another Vaadin 7 version.