I've tried reinstalling the FacebookSDK framework a few times but all that gives me is linker errors.
The #import "GADCustomEventBanner.h" statement is located in the FBAdMobCustomEventBanner.h file. I'm not sure what to do here and I've even tried starting over.
Make sure you are adding the FacebookSDK.Framework folder into your project. If it appears as "FacebookSDK" in your projects framework folder, you did it wrong.