i've changed the suspension on multiple cars, the e36 isn't the easiest, but it's not that bad, you'll need to buy or rent a spring compressor, that's the only special tool i use for the job, other than my air tools, but they aren't necessary, just make it a lot easier, everything else is just sockets, and other regular tools, i'd also recommend getting a buddy to help you out, if it's your first time it'll probably take in the neighborhood of 5 hours maybe less, maybe more, that includes time for stubborn bolts and jacking everything up
good luck with it, if you have any questions we're here to help
also this link will help too
Pelican Technical Article: E36 Performance Suspension/Lowering Your BMW