If you pull in those slides on the top right & top left, of the bottom window, you can swing it out, then turn to remove. Then the top should be able to slide down, and you can then do the same to remove it from the frame, so that it can be taken to a glass shop. Just remember to close up the window, since it can take a day or two for the glass shop to finish up.
That age of a window, I am going to say that they are probably Double pane not single.
That age of a window, I am going to say that they are probably Double pane not single.