the old greddy kits were locked, and honestly, i have no idea if the new ones are like that or not, the only way you could re-program it would be to get the code from greddy which i thnk they only give out to pro tuners or something like that and u also lose ur basemap when u do that. The new ones might be different tho.

Of course, K pro is goin to be the best thing you could use for boost, but you definitly have to pay for it.

If this shop ur talking about is really a reputable shop, i think i would listen to what they have to say cuz they are goin to tell you what would be the best thing you could do for your money. 5 grand seems kinda steep, but that might be what is needed for turboing the k series, again, i dont know much about them.

Probably didnt help any w/ that, but i think i would look more into the custom kit and then do lots of research on turboing ur car. I know its been done already so just try to see what other people have done. I know ive been doin so much freaken research on boosting my car, its crazy, but its really helped out.

I cant really help you more than that. Sorry
Im sure someone will come in here and spread some more light on the subject.
My advice would be to just try and be patient and just dont rush into anything. You might regret it later if you do.