You have to un-solder the brushes from the other side of the holder. Be careful... when the solder melts, the spring inside there will shoot across the garage floor, and then you next post will be to ask if anyone has a spare alternator brush spring!
I have actually acquired a desoldering tool to assist in this very task. It's a spring loaded solder-sucker that fires when you press a button, sucking up any molten solder. Works ok.
