Broken Antenna Removal & Replacement ?s

The antenna mast on my '71 Dart GT was broken during the Woodward Dream Cruise (trying to clear some of that yellow "CAUTION" tape).

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I have since located and purchased a complete replacement antenna (from FABO member Tony (whitepunkonnitro)). I have also borrowed an antenna nut wrench from a co-worker. After I remove the nut, how do I remove the broken antenna (and cable) from inside the fender? Can I pull it out between the door (the hinge area) and the front fender? Or do I need to get into the fender. If I need to get into the fender, how do I do that?

As usual, thanks for all guidance/direction.