I like using RC Hill Mitsubishi in Deland, FL for getting my OEM parts. They consistently have the best prices.
http://mitsubishipartswarehouse.com/What happened to your steering rack? I'd definitely get the reman'd unit, if given the choice.
The junkyard LCAs should work fine, especially with new bushings and ball joint.
Regarding the bushings, it will ultimately save you a lot of time to do them all at once (assuming a corner at a time). I did all the rear bushings at one time, and haven't gotten around to the front yet. And like Toasty said, you'll need a new alignment each time you put something new in, so there is coin to consider too. I've got a lifetime alignment plan for my Gen3 with a local Firestone Complete Auto Care. It was $180 (the price of 2 alignments), but I can have it aligned for free everyday from now until Jesus comes back. Something to consider getting, especially with a Gen3, as their rear ends typically need more alignment attention to correct camber.