Question about replacing antenna on 1990 GMC suburban

Folks, the antenna connection has loosened up at the radio (the center post wiggles around) and I have lost the ability to hear the radio now.
Upon looking at the antenna, it looks as though I will need to remove the grill underneath the windshield wipers in order to get to the antenna to unscrew and remove it and replace it.
I was wondering if anyone could let me know how to remove the windshield wipers in order to get the grill off? I think that the grill is bolted on in the interior of the engine compartment, but I am not sure as to how to remove the windshield wipers, nor how to snake the antenna wire through the firewall. Any help and/ or advice is GREATLY appreciated, thanks so much in advance, Richard
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