Beyond adding 7 cameras, you also need new vehicle harnesses (which are very difficult to replace), and a new AP3 processor. The entire braking system changed as well, so all the brake system components need to be replaced. The steering rack should also be replaced, as it now has redundant power (although early FSD cars didn't have this). Need a new windshield for the cameras, and new side pillar glass on both sides. I'm likely missing something else that is needed, as so much changed between the pre-refresh 2016 and the post-refresh 2016.
You also need to pay for FSD ($15K) and get it activated. If possible, I'd expect the cost to greatly exceed the price difference between your old car and a used car with FSD.