There's a spring loaded fastener on the stalk which is really strong, so just push it back in or pull it out hard. They're designed to come off with a large force, or put back in with the same force.
Caution: Do not remove the mirror face from the stalk, it's hard to put back in. We picked a good one from the yard but accidentally pulled the mirror from the stalk, now I don't want to break the glass by pushing hard just so the stalk ball joint would fit nicely.
Caution: Do not remove the mirror face from the stalk, it's hard to put back in. We picked a good one from the yard but accidentally pulled the mirror from the stalk, now I don't want to break the glass by pushing hard just so the stalk ball joint would fit nicely.