I'm not sure if it voids any warranty or not. I got mine through private seller. But you can find parts at quite a few places. I will list a few for you.
www.trdsparks.com
www.getpaw.com
www.fastscions.com
www.nonstoptuning.com
I purchased my lights from
www.ledunderglow.com and
www.ijdmtoy.com
And you can make your own spectre intake with parts from autozone... heres they DIY for it...
http://www.scionxdforum.com/forum/sh...spectre+intake
The xD is hard to find parts for so you may have to retro fit some pieces. There is not much for the xD if your going for power, remember this is a eco car. Its not built for speed. If your looking for body kits and thing like that just google "scion xd body kits" and click the shopping tab. Theres a bunch of listings there. Hope this helps.