Was told my engine was done. Is there a way to check if it's the whole engine or just a component ?

Truck ran hot and died. Was told by a shade tree mechanic that the either the engine was done or the head gaskets needed replacing. While taking the engine apart he told us it was rusted and burnt up. The truck started up fine didnt make any noise or have any other problems it just cut off. We cant afford to replace the engine so were trying to find out if we have other options.