Where to start???
As far as the ECU is concerned, there are many types out there that do an excellent job. If you have a tuner in mind, go and speak to him to see which system he advises as some are more proficient in a particular brand and he may also tell you which is best for the turbo you settle on.
If you want good results, you will be paying for a decent ECU. If you want to go cheap, get your current ECU chipped or score yourself a piggy-back, like a Greddy e-Manage, SAFC or similar item.
If you're upgrading the turbo, I would advise at least an exhaust, intake, fuel pump, and FMIC.
Have a look here, it may help also:
http://www.skylinesaustralia.com/forums/in...t&p=4467941