Troy Bilt Tb575Ec Head Removal. Pull the trimmer head downward, free from the trimmer spindle head. The eyelets on the inner reel cannot align with eyelets on the outer spool, so the replacement line can.
If you get a reading of one, move the ohm setting down one. Loosen the new trimmer head retaining bolts to spread the head open enough to clear the spindle head stops. As per troy bilt, you should be able to restring the head.