Has anyone know how to remove the metal gas tank filler/vent tube running from gas filler door to inside the trunk at the gasket?

Changing the sending unit turned into frustration with all the clamps rusted beyond PB Blaster help. I managed to break a couple clamps off with a mallet and screw driver, but cannot get to others. I need to replace the vent hose, but cannot get to the clamp at the filler vent side (at trunk rubber gasket), so thought if I could remove the entire filler/vent pipe from inside the trunk, I could pull the vent pipe hose out with it, replace the hose and then re-insert filler/vent pipe.

Thank for any input. When I get done I'll post how to get around some of the frustration of replacing the sending unit with rusty clamps. Also noticed that existing sending unit has right angle pipe for return line and new one is straight and smaller (existing fitting reduces going into sending unit) meaning I'll have clamp on a hose reducer with a 5/16" extension hose.

Gary