Auto Parts: used fuel cap, vacuum leak, salvage yard

Question
Have a 2000 Saturn SW wagon with code for vacuum leak.  Though i start with something simple.

The gas cap seal is cracked, figure i could get a used cap from salvage yard.  Are all saturn fuel caps interchangeble across the entire line or model or specific to model years?  Or even more broadly, across the entire GM line of cars?

But back to Saturns, if it looks like it, it should fit, right?

Answer
    All GM gas caps from any given year are the same.  NEVER buy a used gas cap; all the auto parts stores have new ones and they don't cost a whole lot.  The fuel system is pressurized on these newer cars and gas caps fail every 6 or 7 tears.  If they don't work right the whole system is not working right.