1970's DIXIE NARCO DN 100-5

[Machine Blues]

I am wanting to change the labels on my machine.   I looked on the inside door and I see a metal plate behind each
button (see attached pics, not the greatest) The buttons look like clear plexi glass and I don't think I can get to the label from the front..  but I don't see how I am going to slide them in or
out of the back side.. I took the switch with spring off one of them on the back  and just cant see how to get at the label.  So I put the switch and spring back on and figured I am stuck on this.  Machine works fine,
I keep pop cold,  just would like to change out the labels.. any help would be appreciated.  Thank you.