Try reading this to help with the stuck peeps:
http://www.angelfire.com/retro/fossil/RCT2/PathingSystems.html
This isn't a glitch within the scenario because I have had no problems so far.
Also, to change the scenery selection, go into the scenario editor, click "load landscape" in the upper left corner, and choose the scenario you want to change (it will be in the scenario folder
) It will load with all of the scenery, but no rides. Now you can go back to the object selection and change the scenery, but once you begin to play, you will have to rebuild the rides, including the exact pieces of Thunder Run, which is kind of annoying.[:p]