Tail Light problems of the 2005 Nissan Frontier

I have a 2005 Nissan Frontier with 4,200 miles on it. About a week ago the truck died in the middle of the road. It was still running, but it would not accelerate. This happened one day after the engine check light came on. According to the dealer and the owner's manual,this shouldn't have been a big deal. Anyway, it turned out that I had a crack and small hole in driver's side tail light. The hole was the size of a ball. It had been raining for a few days, and apparently water was getting into this hole. The dealer told me, after 3 days with my truck, that water getting in through the tail light was the cause of my truck breaking down. The only thing done to correct this problem was replacing the tail light. They didn't check for other leaks, or other faults with the vehicle. It just seems absurd to me that a modern vehicle can be disabled by such a minor thing, and had this happened on the freeway there could have been a major accident. What they are basically saying is that driving this vehicle in the rain could cause a breakdown, and all they did was fix my tail light.