If you are talking about the Legacy 990 system, I think you can get a brand new system for another $50 or so more. At least some of the forum sponsors here were selling them near that price point recently. Personally, I would prefer to pay the extra for a new set with something like this, rather than save $50 on something used.
Also, Lionel is good about repairing the Legacy 990s, but I don't know if that would apply to one purchased used? I am certain they warranty the sets purchased new.
I see GRJ agrees, which I take as good advice...he slipped that tin while I was typing...