Check out Corbin's write-up, its strut install walkthrough but you can also use it to remove or install springs. If you're installing lowering springs that are low in spec (H&Rs or Sportlines) you won't need spring compressors, I rented some when I was installing my H&Rs and didn't even use them, no need cause the springs are already short, but I would recommend having spring compressors if you're going to install stock springs.
http://www.2gnt.com/www/corbin/struts.html