Complex sentence: On a trip back to New York in 1958, he met Alan Freed who advised him to change his name, so Johnny Ramistella had a Baton Rouge attorney change his name to Johnny Rivers after the Mississippi River that flows through Baton Rouge.
Split into simpler sentences: On a trip to New York in 1958, he met Alan Freed, who advised him to change his name. So Johnny Ramistella had a Baton Rouge attorney change his name to Johnny Rivers after the Mississippi River that flows through Baton Rouge.