Can they give you more details about what is blocked? Is something blocking your exhaust? A blockage should not require a new engine. Really, unless you actually damaged an internal component of your engine like the pistons/rods/valves/cylinders, you should not need a new engine. Anything that attaches to the engine can be replaced separately. This is very strange that you only throw a code for a cam sensor but you're having all these other problems.
Well, here's the story:
Last week, I burned my starter because I tried to start the engine too much. Meanwhile, while the starter was in the repair-shop, I replaced also the MAF-sensors and had the car transported to a Nissandealer nearby.
When the starter was fixed, I brought it to the dealer on saturday. Monday, they called me to tell me the starter does not work. They said they tried to start 2 times and the starter was broken again, they also said the complete engine was blocked and that caused the starter the break itself. I went to them, took the starter with me and headed back to the repair shop, I had warranty on the repair. When they opened it, while I was there, the damage was huge inside, but where I burned it, now the starter was desintegrated due to high-speed rotations, so basicly, the starter worked without having the engine on it. The guy at the repairshop showed me, with a defective one, what happened. Also, there were signs on the positive power-connector they caused something like a welding-spot (short-circuit). We repaired the starter again, put it on a testbank and it worked perfect.
One day later, yesterday, I went back to the dealer with the starter, they installed it again. When they tried to start, I saw there was no power on the car, no lights and such. We searched and 4 fuses were burned and the main fuse (250A) was also burned, so that confirmed to me there was a electrical error caused by them when they installed the starter after the first repair.
I told them to connect everything the another battery, on my risk, and tried to start. replaced the fuses, connected the battery. All lights on, push start ... and the starter worded perfect, turned the engine ... but same issue ... Engine starts, after 2 seconds it stops ... so the same issue like I had before I replaced the camshaft and MAF-sensors
But, one thing is sure, they did something wrong after the first repair of the starter ... and I getting out of ideas