Estate taxes and donor's tax

Hello, my father died in 1998 and his estate taxes has been paid. However, until now, we have not transferred any of the title to his heirs including my mom. (original TCT has my mom's name on it together with my father's name). I have the CAR that was given to me by the Bir but no one advised me to have it transferred. I am now planning to fix all our papers because we plan to sell some properties and tranfer some to my sibling's names while my mom is still alive. What do i do? What is the process of having the TCT ownership changed and how much are the fees? Another question is, what if my mother suddenly passes away and we have no money to pay for the estate taxes what will happen? Your reply will be very helpful. Thank you.