Assuming I have the correct model #28540, the ac regulator is part # 691ACRGF04 ($30). Lionel's 1/2 price sale is the weekend of Nov 2nd. The grill is not separate from the shell. The shell is only available from North Lima Train Works. Its part # 6208540007 and North Lima has the part for $125.
Since the smoke unit overheated, you may need to replace the smoke unit as well. The smoke unit is part # 6308031200. Its also $30. But you can get 1/2 price on Nov 2nd.
You can check all this out at www.LionelSupport.com