Complex sentence: In 1999, Montano was replaced by current bassist, Dave DeRoo, Garcia was replaced by current drummer, Kris Kohls, and Jackson was replaced by current guitarist, Tim Fluckey and maintained that lineup from 1999 to 2003.
Split into simpler sentences: In 1999, Montano was replaced by current bassist, Dave DeRoo. Shortly thereafter Tim Fluckey joined the band, and maintained that lineup from 1999 to 2003.