I have an 02 WRX that is getting the swap done at Precision Tuning... Some of the stuff I read here doesn't seem right (at least for an 07 6mt to go into an 02). My mechanic told me that you can keep all the suspension things (struts, spring, etc.), the hubs, brakes, and rear dif as well.
As for the DCCD controller, that's definitely not optional, especially if you plan on using a dyno. The car will drive without it, but it isn't recommended in the long run since the transmission is looking for a signal. Without any signal, the torque split can vary in unpredictable ways and make your new tranny go boom.