Ok I am making a barn yard cake for this Saturday and it is an hour drive away from my home, so my question is

Should I put the 3D barn and hay stack on before I leave the house or should I assemble it when we get to the destination?

Also If I assembly it at home what kind of box should I use to put it in?

Another question, when should I put the fondant/gumpaste figurines on the cake before we leave or at the destination?

Sorry so many questions! Any help would be greatly appreciated!!

I would take the time to assemble at the destination. That is the way that I transport cakes like that. The only time I haven't done in that way was this past weekend, and I had used RI to attach the items to the cake.