Good diagnosis on the nitrogen accumulators. I replaced both, drained and renewed the fluid, blew down the lines, and now I have a nice ride. Unfortunately, the previous mechanic had tried to adjust the ride height, I presume to compensate for the failure of the accumulators. So I had a jacked up rear end, similar to a '69 Nova, until I properly adjusted the ride height. For the future, here are my DIY hints on this job:
1.) Buy an extra liter of hydraulic fluid. Spread it all over the garage floor prior to starting. Spray some on your arms, back and hair. This will save time later, as you will normally accomplish this as you drain the system.
2.) The slippery nature of the fluid on your hands will no doubt result in skinned knucles as the rachet and line wrenches slip all over. So use a rasp on your knuckles before the job, again to save time.
Seriously though, it takes getting your carcass way under the car, so use jackstands generously. And the safety glasses are a good precaution when looking up at all the fluid and road dirt stuck to the underside of the car. And a metric set of line wrenches is a must. Thanks for the advice all, and if I can help anyone on this, just ask.

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1989 560SEL
1971 Cutlass convt. (sold)
1978 Olds Toronado (sold)
the rest are boring