I say spring the $100-$150 for a good PPI, find out what is wrong with the self leveling system. Might simply be shock bushings, might be accumulators, neither one is truely expensive to repair. If the shocks themselves need to be replaced, then the price jumps significantly. With the rarity of the 500E I personally would be inclined to keep it original.
'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.