as for installing a stereo into a car.. go to a install shop and buy a wiring harness.. if u cut the wires you will regret it..
I work as a profesional installer and there is nothing like tring to fix someones mess up when they cut out the wire harness..
as for the 2002 wrx let me know if the one from the rs works.. this will help me much on future installs.. seeing that I have not received any information regaurding this car..
p.s. if anyone ever has a q.. just pm me or e-mail i will be glad to help