I wouldn't really consider 400 hp requiring a major turbo upgrade. A Holset HX35 could support that much, probably more, and you can pick those up for less than $300. I believe a Garrett T3/T04E 50 trim will also support upwards of 450 hp for around $600 for a new unit.
I'm actually working on a twin turbo VG30E setup right now and with some low cost Mitsubishi TD05 14B turbochargers could do upwards of 550 whp potentially (though by that amount of power you would probably want a different turbo as these would start getting terribly inefficient).
As far as writeups go... you're definitely stranded there. There has been maybe a handful or less of these swaps done and no one has done a writeup on it. There is one going on right now that I know of but doesn't have any info on how to do it at the moment.
Fitment wise it will be tight but shouldn't be too much of an issue (may have to watch for steering linkage clearance). Wiring will be the bigger pain from what I've read.
Here's a couple videos of the current DETT swap. He's been working on it for over 8 months and I believe might be doing a writeup but it probably won't be till after its running.
http://www.youtube.com/watch?v=QTeBzVfv ... 4Wbw4aoGLM
If I see any more info on the swap I'll definitely let you know.