Timing belt broke on 1997 GST How much damage?

i can answer this question with one Word...

allot.

Answeryou could have bent some valves but you really don't now until you open it up

It really just depends... More than likely you bent most/all of the valves, and any valves that did bend will more than likely tear the valve guides up getting them out, also you more than likely will have to replace the valve stem seals. Not that big of a job, I had all of my exhaust valves burned and had to replace them in my eclipse spyder and I was able to do it all my self, and lap the valves in. The tricky part is putting the timing belt back on and bolting the engine head back on and setting the timing.