They've had helpers since at least 1992. There was an article in the Watchtower stating that the helpers (of the other sheep) were the modern-day Nethinim of the time of Solomon.
Milton Henschel died in 2003, not in 2000.
The Governing Body members resigned as directors of the corporations as of January 2001. Some of the helpers serve in various executive positions instead. Since this organizational change, publications are said to be "published by Jehovah's Witnesses" instead of "published by the Watch Tower Society" (in footnotes and explanatory sentences in publications), and also the US branch is no longer referred to as "the Society", but as the "US branch office" (since it is legally represented by a different corporation—the "Christian Congregation of Jehovah's WItnesses").
There were 13 GB members in 2000: Samuel Herd, Stephen Lett, Gerrit Lösch, David Splane, Lyman Swingle (d. 2001), Milton Henschel (d. 2003), Ted Jaracz (d. 2010), Karl Klein (d. 2001), Albert Schroeder (d. 2006), Dan Sydlik (d. 2001), Carey Barber (d. 2007), Jack Barr (d. 2010), Guy Pierce (d. 2014).
Geoff Jackson and Tony Morris were appointed in 2005, Mark Sanderson was appointed in 2012.