I would not attempt to remove the handle with it in the window frame. Take the assembly out. Put it on a suitable surface that will give you clearance for the roll pin to be driven out.
Have you looked to see if you can just rotate the latch? I believe there is a nut holding it on the shaft. Don't know of it is a splined shaft. If it is, you can just remove it, rotate it and put it back on.
I know they come apart and can be repaired. So you will have success, I'm sure.
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