Does google have its own version of this overture tool? http://inventory.overture.com/d/searchinventory/suggestion/
You could use Adwords for it by creating a demo campain and try the keywords. But I am not sure if google likes that and it's a bit more work. I always look at the overture tool and translate it to Google by multiply it by 6-7 times. Not sure if it is correct but saw it mentioned somewhere
Yes, you can join Google's AdWords program to get access to the equivalent functionality there. You don't even have to join completely, because part of the sign-up process gets you to start your first campaign, so you reach the keyword estimator before you actually sign up. I think it's better to go ahead an sign up, though, it only costs you $10 and then it's easier to do keyword estimates. Once you have your AdWords account, you can directly access the traffic estimator.