Hi,
As far as object import is concerned, if you have .3ds files you need to convert them to either .lwo or .obj. If i remember correctly these can be converted with poseray..or if you are familiar with, and have access to, other 3d modelling software (3ds max, wingz, blender etc.), you can use those to convert.
A quick search of the forum for terrain import will provide other import options and techniques.
Hope this helps...
Chris