Fortunately its quite easy to tell if an E36 has knackered suspension because it will drive like crap, it should feel tight over the bumps but no knocking whatsoever, with sharp but smooth steering that should also be reasonably heavy.
To check rear bushes drive 1 side at a time over a sunken manhole or something, if somethings wrong that rear corner will seem to 'turn' outwards a bit. To check rear subframe, get the car in 2nd gear, about 4k rpm and come on and off the throttle a few times fairly sharply, any banging from the rear and its almost always the subframe bushes. Front suspension is dead simple and will knock and wander if broken.
Brake wear sensor is a common thing, I always take the bulbs out of mine because im too cheap to buy a new sensor lol. Brake pipes are easy to see looking underneath, they can be a little brown/crispy, cover them in grease and they will be fine.
Im heavily into my BMWs and have owned many, so its a long post but they are my kinda car!