First of all, are you just aiming to change the one bearing?
It would be better if you replace both sides at this time. And if you do that, you might find that it's easier to get the other bearing out first. Though I don't think so. I think that the left side is the easiest one to access. Someone can confirm...
There's no reason to suspect that you don't have the factory spacer, yet. Don't know what you mean by slots. There aren't slots in it. There are rings pressed on to it, to keep it in the middle but you won't see these 'til you get a bearing out. It is / has to be pretty much the same diameter, so there isn't much access space. I've used various things as drifts, including a screwdriver with cut-down blade that's bent /angled-out at the end, so that it can get a touch on the edge of the inner bearing ring. Work it bit by bit. Other devices are described in previous threads.