Removing the Dash Panel to replace insulation

Hi Experts,
I am onto a new project now - replacing the smelly acoustic insulation in my '83 240D. This material is a layer of about 3/8" thick with a dark
grey rubber or soft plastic backing. It really stinks so I am replacing it
Already I have the screws removed from the dash panel and am trying to disconnect the slider arm that controls the air flow into the two jets in the middle of the dash panel. The MBZ manual shows a small downturned piece of thick wire that is supposed to be pulled out of some hole or slot to release the dash panel.
I can't see a thing in there and feeling around with my hand tells me there is a 90 degree arm attached to the air-control slider on the dash panel and there is a pin that passes through the end of the arm and also the end of another arm that heads towards the windshield - possibly to damper valves. That pin does not move easily, at least when squeezed by hand.
Does anyone remember the layout and the technique to release this slider mechanism?

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