Better than even odds that it's the triac semiconductor component that shorted out. While it's a $1 component, it's difficult to access/replace and requires soldering. Given labor costs, I too believe it might well be less expensive to replace the controller than to pay someone to repair it.
Obviously time is of the essence since this is a holiday setup. But if at some point in time you want to roll the dice on a DIY repair, ask again and I'll post some photos and instructions on exactly how to replace the triac in a Z-750 controller.
