Don't try the punch in the bottom hole, this will lead to very expensive oil leaking out of the insert. Don't believe it is expensive oil, ask Koni how much to put it back in!!!
The round deal with two holes in it on top is the gland nut. You can make your own wrench out of a piece of 3/16-1/4" flat stock with a big hole for the piston rod and two small holes that line up with the holes in the top. Put some round stock through those holes. Steel dowel pins work great for this. A small tack on each dowel to keep them in and you have a wrench. Clamp the strut in a vise and loosen the gland nut. The insert should come out when the nut is loose. There is probably a section of round tubing inside the housing between the bottom of the housing and the bottom of the strut. This centers the wheel travel and allows you to reach the adjuster.
Mike
PS - Say hi to Lee at Koni for me. Mike Mackaman, knew him in Kentucky before he worked for Koni, great guy.