do you understand that if your parents were joint tenants with g-ma, the will could not distribute the property? The fact it is included tends to make the "joint tenant" statement a bit suspect.
btw: you have no option about "letting" the bank repo the car. G-mas estate can pay for it or it will get repo'd. You have no claim to the car in any way.
btw; they apply for the deficit against the total estate, not just the property in the estate.

