Fair price? check around and see what everyone else is selling this for such as MPS or other salvage yards....i think theres one guy on here who is a ebay junky...he might know..
if you plan on upgrading to stock 5.0 brake setup, yes you will need everything from spindle to the caliper including rubber lines, master cyc/power booster, and your replacable parts such: as castle nuts/cotter pins for the spindle assembly, new wheel bearings with its cotter pins also, and brake pads.
Recommended would be to replace rubber brake hoses, resurface brake rotors, purchase a vaccum brake bleeding kit, and a haynes/chilton manual for proper torque specs and illustrations.
Now before you start you need to take a serious look and ask yourself if you are going to need more stopping power in the near future for any major mods coming your way. This would be a good time to upgrade to cobra brake or bear brake kits that are out.