You are in for a "treat"...about 2 hours worth of fun.
There is a locking collar on the inside that rotates ~1/8 turn and engages two pins in the bezel portion.
Remove door panel
Remove inside door handle assy & rod
Remove door latching mechanism from inside door
Reach up into door, on inside of button...you should feel a cylinder with two "wings" on it - like a wing nut.
Rotate ccw 1/8 turn while depressing the cylinder/spring and holding the bezel against the door tightly.
Parts may fall into bottom of door after you remove the latch assy.
You should find an inside bezel and spring and the intact button assy.
Note the button part may come out of it's "carrier" rather easily but it appears it is not supposed to. Squeeze the rod slightly to make the thing stay together.
You likely will find one of the "ears" is broken off where it locks over the pin on the bezel portion.
Repair of the collar is possible by observing the unbroken side and forming the broken side similar.
Drill a hole about the size needed, maybe a bit smaller, just inside of the original hole/hook thingie. The pot metal is easy to drill/file.
Use a round file to shape a hook into the remaining metal.
Found the assy is so "sloppy" in fit it's not necessary to file/move the opposing hole. Every assy is a bit different, so make sure your's fits well before trying to reassemble it in the door.
Now elicit aid of local arm wrestler to put the thing back together. It is tough to work both sides but it can be done. Best if someone holds the bezel against door while another forces the inner collar on and rotates.
Noticed on spare lock collar the hook is bit different size on one side.
Makes no difference - just file out the smaller hole to fit all. Believe they were trying to guide you in getting the thing assembled properly oriented. Fit yours together several times to see how it fits prior to ever trying in door. Pieces are made to fit contour of door and collar goes only one way as I recall.
Note the little clips on the end of the long rods can be reused many times. They should be put on whatever arm needed then the rod "snaps" into the clip/arm.
Real easy reassembly if you note how rods are routed prior to removal.
Inspect the latch mounting holes to see if metal has broken around holes from metal fatigue. Weld/paint now if needed while it's apart.
The button assembly is held in place with the two center punched spots on the spring loaded shaft. When the high ridges of the center punches finally wear out, the button pushes all the way in. The entire assembly is held in place
with a twist lock rear on the rear of the door. Sometimes these rings get distorted over time due to the spring tension against them. They may fracture, or they may break the retaining ears off the chrome pot metal outer bezel. The locking ring is not the easiest thing to remove or replace. Many years ago, there was a sketch of a home made tool that's used to facilitate the removal and reinstallation of this locking ring.
Door panel must be off, window must be up, and I think you need to remove the door mounted latching assembly. Lay on the floor and reach up into the door with protected arm and hand. You should be able to twist off the locking ring
without the special tool. The tool is basically a piece of thin sheet metal with a couple of holes drilled into it that line up over two dimples in the lock ring, and one pilot hole in the center. You see them when everything is apart.