Will a creditor return my repossessed car, which was taken after I filed my case, if I ask, or do I need a court order?

The creditor certainly isn't going to return the car on their own.  You need to at least inform them of the bankruptcy case and demand its return.  If they still don't comply, you will need to seek a court order against them for violating the automatic stay (or, if this is after your discharge was granted, for contempt of court).