I will start with this first although it does not need to be done in this order, you can construct models in goolge sketchup or other software, these can be moved around in your scene in wax but their parts cannot move. If i had a model of a fighter landing and the landing gear extending i would have to make one model for the fighter and one for each element of the landing gear, although in sketchup this can be one model with a few groups or components to use it in wax the gear and fighter must be separate models otherwise they will be unable to move relative to each other. sketchup models can be found at the google 3d warehouse http://sketchup.google.com/3dwarehouse/cldetails?mid=7e7ef910316459a3b281964dca26f211&prevstart=0
this is a good scifi collection.
or across the internet searching for what you want followed by the word "mesh" example: starship mesh , space fighter mesh .these meshes will be of a variety of formats but wax 2.0 can only take those in "3DS, Quake MD2 & MilkShape MS3d" . so when you have a model you like you must convert it.
IMPORTANT: when making a film/animation one of the first things people will see is your models, a bad or boring mesh/model will ruin a video.
Now we must convert the models to .3ds .