The AI systems that ship with CRYENGINE allow for you to get up and running with our stock AI in minutes, relatively speaking. You will obviously need to change out the behavior that ships with GameSDK and the AI setup, but the logic and ability to traverse the world come stock in the Engine build.
You will find numerous times that you need to control the AI as well and for this reason we have provided developers with numerous control objects that shift the visual and auditory qualities of individual AI in your scene. We recommend looking over the AI section and then playing around with the GameSDK project to get a better understanding of just how flexible the AI system is.