The castle is still there in Stara Lubovna, partly functioning as a museum, partly ruined. It is indeed a couple of hours drive from Cracow and Cracow is not difficult to fly to from the US, through Warsaw. Mieszko is functioning in the Polish language as a first name. Rare, but it is there.
The Piasts were rulling, I would say, closer to 400 years, a bit more, actually, sometime like 966 - 1370 (before 966 it is a bit blurred). The last one, Casimirus the Great, was, as it seems, a pretty cool king.
Hope the Czech site offers some useful information on Mercedes benz.