I had one of those machines in university too and had the same stained/cracked palmrests. That said, I also paid for extended AppleCare and had the whole top case swapped for free multiple times throughout the three years that the coverage lasted.
replyWhen I was a broke student I would buy MacBooks with broken palm rests for a discounted price, drop them off at Apple for a free repair (under extended warranty) and flip them for a profit. Three hours of my time turned into €100 profit. Minimum wage was €6/hour back then.
replyDid the same years later buying up first gen iPod Nano and trading them in for sixth gen because of the battery recall.