I believe what you are refering to is the timing belt. Which belt came off? Since you said the idler pulley did something, I assume you are talking about the exposed serpentine belt that runs the PS, AC and alternator. The timing belt is under the front engine cover and not exposed. Two seperate belts with different functions.
If the serpentine belt came off, no worries. It in itself coming off will not hurt the engine internals. The timing belt, well, that's another story. The 2.5 is an interference engine which means if the timing belt comes off while the engine is running, the potential for internal damage is high.
Overall, from what you stated I don't think you have any internal damage. Correct the known problems and get back out on the trail.