Ryan,
Although I didn't get to ride the GSMRR, I did visit the train museum a few years ago and enjoyed it very much. Not only is it a large collection of Lionel but also American Flyer and Tinplate.
The layout is fun to watch, too...but not as much fun as the faces of the little AND big kids who walk through the door and see the layout for the first time. I was told by the gentlemen operating the trains that the layout was originally built by a pastor in the area. They had to saw it up up into 12 pieces in order to transport it to the museum.
Whether your into 3-rail or not, it's definitely worth the visit...
Tom