I'm not one to push using the law to get things taken care of but to me based on what you said and the timing of events the dealership is at fault. If they took it apart then chances are they weren't careful with putting things back together. They for sure didn't do any diligent troubleshooting considering they released the truck to you with the check engine light on in limp home mode. A stuck accelerator doesn't cause the damage that is being implied so there was something else wrong with the truck from when they released it to you in which lead to the engine failure. Just something isn't adding up at all and if you have someone else dive into it to fix it you might lose any leverage you might have to get them to fix it. Again I hate the sue this and that thing, but I've known 4.6 & 5.4L's to run tens of thousands of miles with the "tick" and no failures.