OK, my little bit of advice is based on the SLS of a W123 wagon. I think they are pretty much the same as the W124, but I don't know if any differences.
First, as I've said many times, a wise man once told me "Replace the accumulators, it's always the accumulators". Seems to be very sage advice so far, as I've had two wagons, and accumulators solved both of them. The 80's was very soft and sagging. Bounced softly. Wouldn't adjust height correctly. The '85 was bouncey, but it was a harsh bounce. Very tooth rattling......
You adjust the height via the linkage from the rear valve assy. Then, the SLS adjusts the height to compensate for weight added in the back. It raises quite slowly usually. Hard to see really.
Others will chime in I'm sure. The SLS is not difficult at all really.

__________________
Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John