Nostalgia

I just got a call from a friend of mine, John, who is a retired electrical engineer and pretty much a genius in my mind. Anyway, on Thursday when my grandparents came over for Thanksgiving, my gramps told me that John was driving to Denver for an annual woodworking show, when he heard this 'thunk' from in his engine. Now, you don't need to be a mechanic to know, any kind of 'thunk' in your engine is NOT a good sign.
Now, let me tell you about John's truck. He has a 1998 24 valve Dodge Cummins. He is anal about vehicle maintenance, so it is damn near brand new as far as wear! It's only got around 175k on it, brand new tires, and is EXACTLY the kind of truck I would love to have.
Anyway, John took it into the shop and had them assess the problem, and they told him that one of his valve springs had broken and dropped the valve in his cylinder. On a normal car, this would pretty much cause the engine to grenade. But, with a heavy duty engine like this, the valve most likely just mashed down into the piston face and put a few scratches on the valve head. So, John called me this afternoon and told me the situation, and told me that he might pay to have it fixed, or he might just sell it and buy something newer. If that's the case, I could pick up a nice 10000 dollar truck for around 1000 and rebuild it. The only thing holding me back from making an offer is not knowing how extensive the damage is. If the piston transferred any force to the connecting rod, the rod may be bent, which may have bent the crankshaft, which could screw over the entire engine. And the cylinder walls could be damaged, the head could be severely damaged and that already is a machine job around 3-4 grand.
So, hopefully the damage is limited to the piston and the crank! I might have to shell out a few hundred for a new head, but that's a drop in a bucket compared to how much I would have to pay! I've got my fingers crossed for sure.