You can remove the old races with a good-quality punch, preferably a long one with a well-defined edge. Don't even think about using a screwdriver: it isn't tough enough for this job and there's a danger of scoring the inside of your hub. Assuming you have thoroughly cleaned all the old grease from the hub (and you do need to be surgically obsessive in this operation!), the inner edge of the bottom of the race is just visible when you look down inside the hub. Flip the hub over to see the edge of the other bearing race. This is a very small target: you need to be precise, and work your way around the race so as to minimize any tendency for the race to wedge itself stuck at an angle. They will come out gradually; take your time with them and then enjoy the beverage of your choice as a well-earned reward. Keep the old races as they make good drivers for the new ones.