If i'm right,
you must of course pay the VAT on the car, plus i guess there is a fee per Kg (but it's quite low).
Then, you must go to the "service des mines" in france, or TUV in Germany etc (depends on where you live) to have your car registered as a legal car in your country. This is complex if the car has never been sold in your country. Otherwise, there is a certificate you can get from the local importer stating the car complies with the countries legislation...
Basically it's the same for any car...