Watched a show on TV once where they replaced one of those giant multi-section antennas just like that one. Four guys working up on the very top had to build a crane scaffold mounted to the tower that went up alongside the antenna. Unbolt the antenna in sections and lower it to the ground using the crane scaffold and a cable from a motor winch on the ground. Then pull up the new antenna sections and bolt them together followed by dismantling the crane scaffold. Scary, scary stuff…

Hmm…found a short vid on YouTube of them lowering an antenna that way…

Youtube Video