560 Rear Suspension

[Hoopster]

I have an 1988 560SEL w/175k on it, only owned for a short time. The Rear Suspension Sags, I have replaced, so far, both rear accumulators (Nitrogen Cells), rear leveling valve, new fluid and filter, but suspension is still not working. Rear shocks are dry and do not appear to be leaking, no leaks from suspension system (fluid level is constant). It apears that the system has not been working for some time as the rubber suspension stops are cracked. I do have a new set of rear coil springs, I have been wanting to tear the rear apart only once so I have not installed them yet, but my understanding is these will not fix problem more of a maintence correction. I have checked the sway bar links they dont apear to be broken. When I manually move the arm on the valve the system does nothing, when the bled valve is opened fluit squirts out so I asume pump is working. Is the problem Shocks? Pump? Sway bar Links? System needs Bled? Has system been damaged from long term neglect?

If problem lies in replacing rear shocks would used ones that have not leaked be ok? or should I pony up the $300 bucks per and get new ones?

What other rear suspension componets should be replaced (ie mounts, bushings,etc.) at this time?

It is also tire time, if I go to a 17" AMG 5 Hole replica wheel/tire combo can I expect any problems such as rubbing/clearance or will they be OK?