24K is wow, too soon. 124K would be more common based upon typical oilhead/hexhead use. Unless there was a spline issue in which case the 75K is a common number.
The dry, car like clutch in the GS and other beemer twins doesn't like slipping. Keeping the clutch in the friction zone is a no-no for clutch longevity. Rough rule-of-thumb: over 2,500 RPM the clutch should be fully engaged.
As for tools... I've not done that job so I really don't know. I'm looking at the RepROM DVD and it doesn't mention much more than a "threaded pin" and a "engine locking device". The locking device is a small wedge that fits between the gears on the flywheel and the case to hold the flywheel in place to loosen the clutch mounting screws. Oh, you also need a way to center the clutch. Don't know how the "threaded pin" is used. The manual doesn't mention the use of guide pins for aligning the transmission. I'd likely make some anyway. M8 x about 110 mm, cut the head off and slot the end.