The fan clutch is what your visco fan blades are bolted onto, which is then bolted to the water pump pulley. It's a really easy DIY job. All you do is unscrew the four bolts that hold the clutch to the pulley. Unscrew 3 of them totally, but loosen the 4th one just enough to get the fan clutch out (they fit in slots, not holes), that way you will maintain alignment of the holes when you reinstall it..and the tension from the PS pump belts won't mess with the pulley. You may have to loosen the tension anyway, you'd just have to see. Then just unbolt the fan from the clutch and then reverse.
Flex discs are rubber pieces that mate sections of the driveshaft. They take up tension in the driveline. If we didn't have flexdiscs, we'd have broken drivelines left and right. There is one right by the rear tranny mount. It's a rubber disc with bolts through it. People do it as a DIY but it's not as simple as the fan clutch. I've personally never done it, but I would guess it's more of a medium DIY job. If you have no or little mechanical experience, I'd think about it really hard before tackling this one.
Just wondering...how do you know they need replacing?
'86 420SE Euro
904 Midnight Blue, Gray Velour
Dad bought it new, now I own it.
"A Mercedes-Benz is like a fine wine, it only gets better with age."