The distance selling act only allows for returns that are untouched so by opening it to test for problems you would be changing that.
You'd be charged a 15% restocking fee for testing a monitor and then returning it, rightly so imho.
As for dead pixels I've bought personally nearly 50 tft's and I've only ever seen one with a dead pixel, are people really that anal about things. If you are there are the class one displays.