Are you from France or Belgium? Since the Glo is less than one year old, I think the warranty is still going on. In some cases the fact of buying a device second hand will void it, but I'm not sure if that applies in France, in Belgium or for that sort of products.
When buying from FNAC, there are two sorts of receipts: one is a plain one from the register (no name on it), the other one is more detailed and includes the buyer name.
If the seller can provide you something close to the first one, no one can know you're not the original buyer.
Regarding your questions, it's hard to tell for sure, but the screen looks good on the pictures. As said previously, a close up of the screen at full brightness would be a good idea.
Good luck to you
