Used replacement retina screen condition

Hello everyone,

I'm planning to replace the screen of my Mid-2014 15" MacBook Pro with Retina Display, and I've come along iFixit and found it quite promising. The only thing I'm worried about is the quality of used displays. I'm replacing mine because of a large scratch that is noticeable a lot on bright backgrounds, and I don't want to end up with another used display with scratches on its surface. Does A-Stock mean that the display is in a new-like condition without scratches? In what way are they "used" components? I'd like to know what exactly to expect from used parts before purchasing a replacement part worth $400...

Thank you in advance, answers will be highly appreciated.