You can buy a K&N filter from
http://www.subaruparts.com, I believe its about $50, but I believe you are looking for a cold air intake (I don't know who makes one for the SVX). I would check this site though before you buy one, it describes how the filter will actually reduce performance
http://my.voyager.net/~tmclane/index.html but if you do put it in it should be easy to do, it just goes right on. My friend put an air intake on his truck with no problem, the filter/intake should have instructions with it to install it.