I'll be finding out how to do this in a S124 shortly -- I suspect the proper way is to take down the center bearing after removing the bolts on the flex disk (front) -- should just give enough clearance to remove/replace the disk.
On the older models there is a nut under the rubber boot beside the center bearing that is loosened, allowing the front shaft half to push back.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!