Aluminum heads aren't as prone to cracking as cast iron heads. However, they will warp up like a potato chip if you overheat the engine enough.
Pull the head, take it to a machine shop and have it decked. Check the block for cracks in the area where you see water leaking. Unless you ran it screaming hot, you probably just blew the head gasket. If it froze and cracked the water jacket, you could well be cracked into the cylinder wall as well as the outside of the block.
Cracked block=mucho more $, as you will be buying an engine.