Are you using the original NR2003 MOD for the import? Are all the game patches installed with the fresh install? Hard to determine the issue with so many factors that could cause this.
I'm starting to believe it has something to do with the compression (or in this case, lack of) of the .car file, but it's just a theory given by the fact that I tried to attach that file to my previous reply but it gave me an error in a pink background with red letters that says "disk quota exceeded," (amongst many other words that is more like a really large code or something) and I have the screenshot of it but I can't upload it either, tf? Feels like the servers are malfunctioning in here.
Now, to answer your questions.
1. I don't really know what you mean by the original nr2003 mod, are you talking about the base game? As for that I think I can only mention that I'm using the SNG 2003 - 2005 mod, but with a 2006 carset (this paint scheme I've made is for said carset)
2. As far as I'm concerned, I did install everything that I need