general problems of the 1997 Audi A8

We want information regarding the odometer "rollback" (changing from kilometers to miles). Does this constitute odometer fraud if sticker was not on the door when we purchased this vehicle? we want to know if all legal requirements were met for importation to the u. S. From mexico in 1999. And were all taxes and/or penalties paid in full? also were all document requirements complied with? vehicle id number is not on the dash on left-hand side, visible from outside.