I would like to tell you to take it back. It is tuff when it's not right out of the box. I will usually dive inside to see what's going on. The Lionel design is a little different and I believe the trucks are removable with a 90 degree twist. Maybe something is bent?
I don't work on Lionel very much. Their website has diagrams that could show you of something missing? They answer emails and are very helpful too.