Airbag question

[xtreme patrol]

If I may ask. I too have a Airbag question my light just stays on all the time from the moment i start the patrol it never flashes.
It started when my alternator crapped itself about 10 months ago I needed to replace the ECU, ALT, Airflow meter, instrument cluster, stereo, all globes inside and out, most fuses, power antenna and my central locking is still not working
Auto elec said something fused inside the alternator and it sent something like 24 volts to everything
Sooo where to start i don't want to poke around to much nor do i want to let Nissan bend me over im just guessing that its the control unit thats fried like the ECU did. Can i just buy one from the wreckers and plug it in? or do i need to buy lube for my visit to Nissan LOL