Is it fine to change an odometer?

Answer 1

No. In most states it is a crime to tamper with a vehicle's odometer or hour meter.

You can however replace/repair a defective odometer if you document it.

Motor Vehicle Cost Information Act, 49 U.S.C. Section 32704

1. (It shall be unlawful for a person) "with intent to defraud, operate a motor vehicle on a street, road, or highway if the person knows that the odometer of the vehicle is disconnected or not operating; or
2. The owner of the vehicle or agent of the owner shall attach a written notice to the left doorframe of the vehicle specifying the mileage before the service, repair, or replacement and the date of the service, repair, or replacement.
3. A person transferring ownership of a motor vehicle shall give the transferee the following written disclosure
   1. Disclosure of the cumulative mileage registered on the odometer,
   2. Disclosure that the actual mileage is unknown if the transferor knows that the odometer reading is different from different from the number of miles the vehicle has actually traveled.
      1. Mileage Statement Requirement for Licensing. - (1) A motor vehicle the ownership of which is transferred may not be licensed for use in a State unless the transferee, in submitting an application to a State for the title on which the license will be issued, includes with the application the transferor's title and, if that title contains the space referred to in paragraph (3)(A)(iii) of this subsection, a statement, signed and dated by the transferor, of the mileage disclosure required under subsection (a) of this section