Mirror repair.
Once the black trim is off you will see little dots (like pin heads) where the glue was, superglue will set it back in place once you reassemble.
Use a sucker on the glass to lift it from the housing, the mirror glass is thin and will splinter easily if you try to lever it out.
Don’t misplace the spring with the snapped bolt head that is in the casing, you may need to re-use the spring if there isn’t one in the repair kit.
My mirror fixing and pivot on the Eunos was slightly different from what you have shown in the photograph.
The mounting block that remains on the door has a plastic cover that unclips to reveal the fixing screws for the mirror mounting, (carefully pry it from the lower edge to ease the plastic cover off), the screws will be revealed and no doubt be rusted into the captive nuts (on the inside of the door panel).
If you can remove them and detach the mirror mounting it makes the repair and reassembly easier to do with the repair nut, bolt and washer set.
If the mounting cannot be removed then you need to take the door panel off and put the bolt through the mounting housing from inside the door, and mirror stem and put the spring, washer and nut on and tighten. After cleaning grease the black ball joint and the socket (pivot cup yours looks corroded), you may have to rub it down.
The original bolt had flats crimped into its shaft so that it could locate in a cross cut into the black plastic socket ball (used to position the mirror when turning the mirror inwards against spring tension) you will see the cross in the black plastic ball socket when you clear the dirt out of it.
When you tighten it you will have to decide that it is tight enough to hold the mirror in place, but easy enough to adjust, but not so tight that it starts to seize up again.
The new bolt or screw may not have the crimped tabs, so you may have to tension it a bit more as there is no physical tab to locate it in the cross of the ball socket.
The replacement bolt is usually stainless steel so won’t rust and break like the original.
Hope this helps.
Steve W