Complex sentence: The assembly line closed in May 2017 with a very low production rate for a few years, after 470 were produced in 12 years it is replaced by the Cessna Citation M2 as the entry-level jet with nearly 150 produced since introduction in 2013.
Split into simpler sentences: The assembly line closed in May 2017 with a very low production rate for a few years, after 470 were produced in 12 years. The Mustang's place as Cessna's entry-level jet is being taken by the Cessna Citation M2, of which nearly 150 produced since its introduction in 2013.