I would definitely return a computer or notebook with even what is classified as "cosmetic defects". I suggest in future purchases that you really look the thing over before handing over cash/credit card. Not possible via online, so your only option is physically going into stores.
If there's cracks and stuck pixels, what else is wrong? Hmmm....not to put a curse on you or anything, but will the hard drive crash? Will the processor fry, a common used-laptop complaint? Will there be claims of memory buffer errors because the previous owner didn't install the memory correctly? Will the backlight in the LCD go dead?
Be really careful when buying a used laptop, or anything used, and even new, in that case. It seems to be that people only take a long time with research and inspections when buying a car, but anything else--a house, a washing machine, a computer...they want to get it done and over with.