Thats very unfortunate mate sucks when things like this happen.
Might as well go forged pistons at the very minimum while the motor is all out imo accompanied with new water + oil pumps, oil restrictor and a sump baffle as you would be silly not to.
I remember when doing mine I had the car dropped the car off Saturday morning, picked it up 2 and a half weeks later with all machining, assembly done and few other goodies I dropped off installed and a retune. A year later my car is still going hard and pulling rather respectable power figures with no issues and the motor runs beautifully. If you want details etc shoot me a PM I will be more than happy to give you some more info
Ps. Why on earth would you make your GTR a daily, thats just asking for trouble lol !