I repeat again, this dent was present 6 months before there was any problem with the screen.
In summary what everyone here is saying that:
a) Dents are not common in any of the MBP models, and definitely not in late or early 2008 models. The guy or girl who sold this to you, didn't take proper care of it.
b) The screen falling apart, could be related to the dent or could be because of more misuse. 6 months or not, this type of damage is not common in any MBP models.
c) There's no easy way to "fix" this. So, you have three solutions: i) either sell the parts individually on ebay or something, save some more money and then buy a refurbished. ii) watch youtube or ifixit and see what DIY options are for this type of damage. OR iii) use a duct tape.
There's no other magic to this.