[Tezcatlipoca]

Nothing wrong with buying a Sky box off Ebay or anywhere else - they're not Sky's property (unlike Virgin Media boxes & modems, which shouldn't be sold on ebay as they're still VM's property).

You would need to get a dual (at a minimum) LNB fitted to the dish though, as Sky+ requires two feeds.

You *would* have to ring Sky - it won't just simply work.

But, all it would involve is phoning Sky, telling them you have a new Sky+ box, & asking them to pair your viewing card with it & activate the Sky+ features.