Thanks for the info. I'm not sure what I can do about the mirror issue, but I will bear that in mind. I have seen that before too. The trouble is if I increase the clipping distance for the image rendered from "behind" the mirror, it might miss a part of the side of the car.
The page screen shouldn't really be so long, usually. Alarm bells are ringing! Is it necessary to use so many separate textures? Usually only repeating textures need to be on their own texture page. It's more efficient for most texture cutouts be be on a shared page with other texture cutouts (as you see in the official LFS cars).
But anyway, there is a text size button "text" down at the bottom right that may help, if you reduce the text size, you'll see more pages on screen.
I don't know why smoothing groups have been lost on your model, I haven't heard of that before. Have you tried "compress groups" in subob mode? Maybe the originally imported model has an 'illegal' number of smoothing groups.
Clean object gets rid of excess unused things, like unused mappings or unused texture pages, etc. Magic triangle sort tries to sort the triangles in such a way that further away triangles will be drawn first. This can help with alpha sorting and sometimes Z buffering.
There should be descriptions of the buttons down at the bottom of the screen when you hover over almost every button in the modeller (but not the vehicle editor, yet). If you are not seeing the tips, maybe your text is too big?