It might be that 5% of the electronics that gets you.
From my experience swapping parts but involving a conventional key blade for an 03 Maxima:
1. I swapped the door lock cylinders as well. This is to ensure the ignition was matched to the door.
2. I swapped the steering column with the ignition as this is where the key's transponder antenna module was located. I suppose the equivalent component for a smart key would be the interior antenna
3. I swapped the ECU because that, from my reading, is usually matched to the transponder stuff.
If not, you could just have a dealer program the ECU to accept the key ID that the antenna sends to it, then just swap blades.
Oh, and congrats on the success so far
