Let me throw in my 2 cents as a modeller that uses 3D Studio Max 3.1 and 4.
By the looks of it those cars have been created with a moderate poly count, and then a meshsmooth modifier was applied. This doubles, triples etc the number of polys on an object to effect 'smooth it out'. If this modifier is applied on the 3D Cafe model, you may be able to delete the modifier, and return it to it's original count. The way I'd do it though is recreate the car, in max, over the old one. Just in low poly form. use the first one as a reference (references of every side of an object are hard to find, so a model is good to use) and create it over/next to the old one. Obviously you have to be able to use Max to be able to do this, but it's just what I'd do.
With regards to your troubles Starstreams, the maps it searches for are the textures that came with the model from 3D Cafe. Also I'd say the DLLs are either custom and could be found at the site, or are with a different version of Max. The DLLs look like they control the kinds of animations (I have no idea what's animated). I used to frequent 3D Cafe quite a bit, it's got some handy textures, tutorials and models to use as reference. However, the models that people post there are like my old ones with a poly count over 30,000. They're not really useful for a mod/game.
Anyway I hope I was some kind of help.