Best way to evaluate the suspension is to just drive the car. The ride should be supple - that's a good word to describe it. The suspension should feel equally firm front and back. If the rear end rides very hard and/or makes unpleasant funny noises, then it has some kind of problem.
If you bring along a couple of friends and a yardstick you can test the self leveling ability. Just measure the bumper height unloaded, then pile said friends into the cargo area. Give it a minute to level, and measure the height again. Should be within an inch or so of the unloaded height.
Visual inspection pretty much amounts to checking the struts for oil leaks, checking the oil level & clarity in the reservoir, and checking the tandem pump for leaks.
If this car hasn't had the nitrogen accumulators replaced yet, it's due for them. They wear out with time, not milage, and 10 years is about it. Figure about $200 and a couple hours for DIY.