Reposession of Motorhome by private party Title Owner from Registered Owner

[MissyinGalt]

California: My father purchased a motorhome. The dealership put his name as the lienholder and his then girfriend's name as the registered owner per her request via phone without my father's consent. Small Claims court has found my father's legal ownership on the vehicle to be valid (as she recently sued him for legal ownership of it) due to bank records. My father now wants to repossess the vehicle to sell or consign it or sell it to someone who is willing to reposess it themselves. She has not made any payments for this vehicle since she left and took it with her. Originally, my father purchased it for the two of them to travel around together in. When she left, they agreed she could take the motorhome if she kept it licensed, insured and registered, and she paid him for the cost of the motorhome (over $10,000) within one year from the date she left. It will be 2 years in November. Attempts to contact her have failed. No money has been paid to him. She has allowed the registration to lapse for several months before paying DMV. She claims to have been involved in an accident with it where she also claims she totaled it and the insurance company owes her $2,500 for it. She drove it to court, by the way. My father has a set of keys to it and the original title paper from DMV. She also claims to be living in it in a motorhome park. So...

Can he reposess this motorhome without a written contract?

If so, how does he go about doing this? (I know the papers to fill out at DMV, but how do you actually take posession of the vehicle?)

Is it an option for him to sell title of this motorhome to someone else that is willing to reposess it or collect money due?

Thank you for your help!