Then a 4- or 5-mm allen wrench, and maybe a 6-mm to take off the top cap. You have a threadless headset- you remove the top cap, loosen the clamp bolts, then the stem slides off the steer tube. unstack all the stuff until you get to the top bearing ring, remembering the order, then you can slide the steerer tube out of the head tube to expose the lower bearing ring.
Have fun. Keep it all clean, and use plenty of new grease.