I'm not sure how long it ran after the sound was hear. From what I can tell the truck has been sitting since 2005. If it wasn't for the noise this truck would be in near showroom condition.

Since it was just the balance shaft chain that broke the balance shafts stopped spinning and those bearings are still good. The engine runs, but as soon as we heard the noise we shut her down.
The main chain remained intacked, and the engine remained "timed". Based on the five or so seconds we had it running I'd say the valves are intacked.
You can also turn it by hand with the pully, but there are... noises. Since the engine runs I'm assuming that I didn't seaze any bearings. Since the oil pump went right away I don't thing there would be any metal in the motor (other than the oil pan).

I like the idea of cutting open the filter, that should give me some ideas of what might be wrong.

The balance shaft kits I've seen online have a single plug, a bearing and a chain. Do I simply leave the upper balance shaft in? How screwed is this motor?