Obviously the plane will be faster with a 120 on it but you are allowed to reduce the throttle. The biggest difference will be on takeoff due to a shorter takeoff and better climb but there will also be more engine torque to fight during takeoff. Prop will probably be slightly larger which will reduce ground clearance a bit. Once up and flying you won't really notice the extra speed all that much as far as being harder to handle. The time to turn around will just happen more quickly. Again, use the throttle. It may not want to slow down for landing as well either but you can do a few things to improve that too.