Complex sentence: On January 13,2014, the band's publicist Liz Rosenberg announced that Christine McVie would be rejoining the band, who quit the band in 1998 after three decades, also announcing that a new album and tour would be forthcoming.
Split into simpler sentences: On January 13,2014, the band's publicist Liz Rosenberg announced that Christine McVie, who had previously quit the band in 1998 after three decades, would be rejoining. Rosenberg additionally announced that a new album and tour would be forthcoming.