Around $550 - $600 for 4 - silver-cad disks and calipers. More for stainless calipers. Call Rodrigo at Century in Wilsonville. Another $120 for a new actuator if needed. If your actuator has a removeable orifice at the outlet, you can remove the orifice and use the existing actuator.
It is a DIY project if you can use a jack, lug wrench, socket set, and can seat races and seals in hubs. Not difficult, just takes a while building each hub, greasing hubs, and bleeding brake lines.
You may need a brake line upgrade since you will need soft lines to each caliper to allow them to float. Drums have hard lines to each caliper, but for discs you want a soft line. You could upgrade to all soft lines - another $100 or so -
http://www.tiedown.com/abline.html . But, you can also just add 4 flexible lines from an auto store.