Friend passed away, and you tried to remove his name from the Jeep title and get a new title in your name only??
Someone passed away and their family successfully liquidated an asset without notifying (orpaying off) a part-owner.
Not trying to start a bickering war here, but that is the other side of this coin, and it is just as damning as your phrase I quoted. I think OP may have more legal standing than the deceased's family seeing as they in fact have now sold the Jeep. They easily opened themselves up to a lawsuit doing that.
Like you say though, 100% a civil case