www.importparts.com sells Drag kits at a pretty good price and will match any competitors price.

www.ks-motorsports.com has an AWESOME build your own turbo kit.

Drag kits are a good basic kit that includes pretty much everything youll need to run 6PSI. They go for around $2900, give or take.

Its hard to answer such a general question. Do a compression/leakdown test on your GSR first, and if everything checks out OK, go ahead with the turbo kit. You're ok with stock injectors @ 6PSI, but if you want to increase the boost, or even if you dont (I would do this anyway) you should look into a Hondata. www.hondata.com can answer all of your questions concerning that.

In terms of the turbo kit...try this site:
http://www.cse.uconn.edu/~yelevich/turbo/turbo.html