Complex sentence: In addition, now the sacred ministry was the only one institution that should deal with the missionaries and the common property of the Native Americans who had worked in Spanish missions "was supervised by the Spanish Justice" or the mayor.
Split into simpler sentences: In addition, now the sacred ministry was the only one institution that should deal with the missionaries and the common property of the Native Americans who had worked in Spanish missions. This common property "was supervised by the Spanish Justice" or the mayor.