Don't restore the dial but try to ask for a NOS dial. Well... they may still have it around... you know... anything magical can happen with Patek.
AND
Keep the old dial untouched.
However, even they do have the NOS dial, I am not sure if they allow you to keep the old dial...
Anyway, I would suggest you to contact Patek (Geneva) directly. I am sure that they are more than happy to discuss with you about the restoration of your 1518. They may come up with solutions that you may never think of.
Remember, contact Patek in Geneva. I have a feeling that they care their watches more than anyone else.