A lot of the first-generation white MacBooks have an issue with their enclosure. It is very susceptible to staining. The palm rests, keyboard keys, and other parts of the enclosure (even screen) can all be afflicted, and it will even blacken sometimes. This was a fairly well-published concern shortly after their release, and Apple was replacing the top enclosure pretty much no questions asked.
Apple published a very short note on it here:
About white MacBook palmrest area
You may want to call and let them know. Maybe they will replace it. The first thing out of the rep's mouth will be that it's now out of warranty. Mine was only slightly out of warranty, but I told the rep that this was a known defect Apple had published an article on, and that my understanding was that this defect was being fixed in or out of warranty.
However, you're now one year out of warranty, which is quite different than just a couple weeks, and Apple can't be expected to hedge enclosure stock indefinitely, so you may or may not have any luck.
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