Re-syncing with Nistune is very simple. You need a Nissan Consult cable and either H-Dev or Nistune software. Any tuner using Nistune will do this for you on request anyway.
If you want to keep your original ECU safe, run with that now and leave it alone. Buy another similar NATS ecu, (same part number), install your Nistune board in that ECU and and re-sync it to the car when you need to.
