placo1- you have come to the right place for active 500e feedback
wow- can't imagine what the total cost will be to bring this car back..
my general initial impression of this vehicle, based upon your list of "to-do's" is that the previous owner was not diligent in keeping the car up and that the car has had a relatively hard life (with possibly a lack of maintence) for all these items to need attention right away
...based on real mercedesshop owners enthusiastic experience posted here (drags, tracking and auto-crossing) seems like the 500e platform is adequately robust to offer this fun absent suspension, rear-end, and tranny failures
is the car modified in any way? often times, hyper-mods in one area affect the less-robust OEM stock-duty parts causing premature failures
have you pulled a car-fax for the history of the vehicle? it may have tons of useful pre-purchase info for you as well , did the dealer pull a MBnet inquiry for you to review as well?- (usually free) any warranty on the vehicle?
my feeling is that once these items are repaired, you'll not have trouble with these items for a while- ..notwithstanding- the suspected previous enthusiastic use of this car may have other parts worn enough not to be detected now- but-in the near future require $$$ replacement as well (an unavoidable bit of risk in used car ownership)
re: your Q's
>the power steering leak issues seem to be common, there seem to be a couple of posts of 500e owners replacing struts,
>fyi-...be very cautious of 500e's that go into limp mode- we have a couple of owners in an ongoing exercise endeavoring to source its cause (but we have a few owners that have happily fixed this ill too)
my '94 E500 (37.8k) required replacement of the the rear self leveling sytem nitrogen spheres recently and also a couple of cam seals due to oil seepage (using dino oil). Other than that, I'm satisified that its been trouble free and offers an enjoyable motoring experience at all levels.
in the event that this is not the car for you, there appears to be a healthy number of 500e/e500 candidates to review for purchase @ ie (autotrader.com)
good luck and let us know what turns out
PS- where is the car at?