Tell your buddy to save his money lol..
But truthfully, ask him what his goals are. IIRC, most XA/XB/Vitz people arent seeing a huge improvement over stock because they're typically limited to 5-7psi since the compression is a hair over 10:1 as it is. I've seen numbers ranging from 150-160 with stock internals and clutch, which is a jump from the 100'ish hp stock, but nothing to brag about.
Seems most people just seem to be running Greddy kits, but there are purist TRD kits you can source from Japan as well. A quick search on the Scion and Toyota boards leads me to this website that almost everyone seems to be buying from:
http://www.turbo-kits.com/xA_xB_turbo_kits.html
It all depends on what his power goals are that determine what mods need done. There's plenty of aftermarket support, but the link above is just a general bolt-on kit that seems to hold people over for the most part. At the very least, I would recommend a clutch.