The motor will slide right into the empty position, it is super easy. However you will need to remove the new brush from the motor so as to reinstall the bottom plate. After that reinstall the bottom plate then the brush again.
Play with the dogs that are you reason for buying a Roomba!
Your Edge-Sweeping Brush needs to be replaced about once a year. Use this guide to learn how to replace the Edge-Sweeping Brush on your Roomba i7. What is the Edge-Sweeping Brush?