Get them to turn all the lights off in the store, preferably go in when it's dark outside. You won't see anything under bright shop floor lighting, which will mask most issues relating to back light bleed and glow. If this isn't possible, go in with a blanket/sheet or VERY large cardboard box and try and create as dark an environment as possible to view the monitor. This may sound extreme, and it might not replicate your real world viewing conditions exactly, but it will show you the worst case.
As for stuck/dead pixels, this is certainly something to check for. You just need to be quite methodical in your approach to this, looking very carefully and closely at every inch of the screen. Just Google image search if you don't know what to look for, but it's quite evident when you see one. It REALLY helps if you can get the screen displaying solid colours. For this you would need to hook up a laptop or PC to the monitor, and either bring up some solid images of colour from a USB stick/hard drive, or go to a website such as this...
https://jasonfarrell.com/misc/deadpixeltest.php
You will be able to cycle through the different colours, seeing them full screen. This makes it FAR easier to spot any pixel faults. You should also look for any dust/dirt behind the panel using the all white background.
Good luck!
