Sorry that's wrong, the coilpack has not killed your engine. The garage are either talking shite, or there are other problems. Ford coilpacks are VERY common for failing, especially on the zetec se engines (Ford only do 2 different coilpack for all the zetec range iirc) Know of many, including mine that have started failing, but have done no damage to the internals of the engine.
The engines actually appeared in the mk4 Fiesta, so late 90's onwards, and were co-designed with Yamaha, and made by Ford. You're correct, they are disposable, but are so common they can be picked up from a breakers for a cople of hundred quid, that is if yours is really knackered, something I doubt if it's just the coilpack that's given up the ghost!