They aren't too bad. They take up the same foot print as two videos $400 is a good price for one with new parts. Those pads that they replaced are something like $20 each. Mine gets a lot of play when I have people over. Usually more adults than children.
I figured out mine mostly by just taking it apart and just trying to adjust stuff on it to play more in tune. Avidcollector brings in parts for these also, you just need to ask him.
100 is a great price cause it's worth quite alot restored. I got mine for $250 in crummy condition.