Here is the info on the current free Garage Band.
https://itunes.apple.com/us/app/garageband/id408709785?mt=8
Now with the drums, do you just play them with your fingers on the screen, or can you actually have drum kits running while you plug in and play your guitar too?
Either way. They have a feature called Smart Drums that will let you pick what drums you want and the beat by dragging and dropping or you can have GB generate some beats for you. It also has a smart keyboard feature that I used a lot.