Although its an old topic, I thought I'd give up some info on the gt28rs, aka 'Disco Potato'.
I'm not sure exactly how much better it is than the gt25r, (whichcan be had for 1080$ from cheapturbo.com), but the gt28rs wasalmost the same price at 1170$ from:
http://www.trickedoutms.com
Also, there are some installation instructions that can be found from sport compact car at:
http://www.sportcompactcarweb.com
And lastly, garrett's specifacations for the turbo are: