Just how THIN is the griddle plate on that Star unit?
Usually a griddle plate is pretty thick. I can picture an element welding itself in place, but a good scraper or even a chisel should cast off the slag and old element fragments fairly efficiently to get it out of the way.
If the bottom of the plate is damaged, just shift the position of the new element over a bit.
Do you have a picture of how bad it is?
Also, I suggest you replace the related thermostat as well. It took a pretty big electrical hit of current and may be damaged from the current flow well beyond its designed limits.