In MN, the gift to your brother of the vehicle will depend on how the Will is written and if it is in the personal property memorandum. It may be that the loan will be paid off by the estate and possible that it is not and goes with the gift as mentioned in the previous post. You should take the will to an estate planning attorney near you to get your real answer (Perhaps the attorney that helped you get appointed as PR). Best wishes.
Unless the will said your brother was to get the vehicle with the loan paid off, then he gets it with whatever loan it has on it at present. He can keep it as long as he pays the loan off on time as nobody will know your Dad died as long as the loan gets paid.