[California] Grandmas brother passed with no will. How do I take over his car loan and keep his car?

I’m trying to take over the car loan that my granduncle had, but he didn’t have a will setup at the time of his passing. I was advised to fill out a petition for probate form and take it to court.

The balance on the car loan is about $3k and the value of the car is around $9k.

Assuming there are interest that had been charged on the loan, would it be worth to take the time to process the petition for probate and how is the process like exactly?