If you don't want the 8-hour limitation of SkethUp Pro demo, you can do one of 2 things: buy SketchUp pro (please don't, it's $500 for something with extremely limited design capabilities), or use 2 computers
. I suppose the other option is to find someone with some way to convert between the two formats (or the other formats that free SketchUp exports to... .dae and something else I believe) and run that through Anim8or.