Complex sentence: Baker's first successor Monsignor Joseph Maguire, took charge of the efforts to refurbish the structures, replacing the original marble towers with the lower, enclosed, copper dome-tipped towers that can be seen on the basilica today.
Split into simpler sentences: Baker's first successor, Monsignor Joseph Maguire, took charge of the efforts to refurbish the structures. He had the marble towers replaced with the lower, enclosed, copper dome-tipped towers that still top the basilica today.