Complex sentence: Before the group began touring to help support "Blues for the Red Sun", bassist Nick Oliveri either quit the band or was fired and replaced him with Scott Reeder who had previously played with The Obsessed.
Split into simpler sentences: Before the group began touring to help support "Blues for the Red Sun", bassist Nick Oliveri either quit the band or was fired. He was replaced with Scott Reeder who had previously played with The Obsessed.