Replacing the flex disk is pretty close to plug and play. You might have to loosen the big 44mm nut at the centering sleeve to slide the front half of the shaft rearwards. I say might, because sometimes there is a little less tension and you can slide it back without loosening.
The flex disk is mounted with 6 hefty bolts (19mm head), 3 go though the drive shaft flange and 3 through the tranny yoke (another piece you have to replace if you throw the shaft). The steel sleeves in the flex disk fit into recesses in the yokes. Torque is 65Nm I believe.
To check the center bearing you'll have to open the tranny tunnel. To remove the shield you may have to lower the exhaust system. Remove all of the bolts, don't forget the two at the rear which are out of sight perpendicular to the rest.
Hope this helps.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.