Hi benito, one connect box is for using apple tv and apple remote, for example, without it it's a TV, with the box it's a SmartTV and does a lot more.
So how much a showroom device is worn, I don't know, depends on the case, usually they are as good as new, it should be in the description. Unless you have a display, the rest is up to you.
Have fun with it, it's a good device, I liked it. Of course it's custom, check it out in a showroom first.