AdWhirl isn’t updated anymore and was taken over by Google, so the Google AdMod SDK is what you should use now, it is pretty much the same thing with the ability to select iAds AdMob etc, just updated.
It’s pretty straight forward adding it to Cocos2D-X too. I put the AdWhirl in a Cocos2D-x v1 app a while back, the newer Google version should be the same. In your “didFinishLaunchingWithOptions”, after your app is “run()” initialize your ads and “[viewController.view addSubview:yourGoogleAdsView];”. See the docs here: https://developers.google.com/mobile-ads-sdk/docs/
I’d also recommend you should consider something like RevMob (https://www.revmob.com/) or Flurry (http://www.flurry.com/AppSpot_small.html). I’m just putting RevMob in my game now and was pleasantly surprised I had a test banner ad displayed in under an hour (they say 10 mins, but I add playing with the sample and skimming the docs). And more like 8 hours to implement it properly in your game. I haven’t released anything yet but I read on various forums that earnings are a lot better than with just iAds and AdMob, along with promoting your app in other apps.