I don't know. I haven't had to make a warranty claim.
That would be a grey area. For example, if the "H" key stopped working, i don't see how they could blame it on the dent. But if your video got distorted, maybe they would try that angle to avoid the claim.
That said, in my time working at Apple, I saw some pretty beat up machines get warranty work done. They generally don't look for excuse to avoid a claim, unlike some other manufacturers. I am sure many will debate that point, but i am speaking on my experience.
I have this exact model. Of all the laptops I've owned, this is without a doubt the best laptop Apple produced (up to that point). It's rock-solid, great performance* and a really attractive model. I have no comment on the price max has set, nor do I know him (her?) nor the condition of the gear. My comment is on the model in general terms.
Putting a larger hard drive in this thing is ridiculously simple (it's under that latched door in the photo above) - mine was upgraded last summer to a 500-gig.
My only suggestion is for anyone considering using this model with Snow Leopard, also budget for an upgrade to at least 4-gigs (or more - pricing for 8-gigs via 2 chips can be had for about $130+tax. I personally recommend CanadaRam).
Good luck with the sale, Max. I fully expect mine to be in the family for several more years, handed down to my wife and (who knows?) maybe even my 1-month-from-birth son!