Just got the shop to replace a head gasket on our old family van 1995 ford winstar 3.8L it had head gasket problem and been park for 3 year, I finally had time to come home and take to the shop getting fix for him , we keep it since new and my dad do not want to sell it, event thought the head gasket job cost more then the van worth. anyway the shop change the oil and filter, and im plan on doing couple oil change after that. Should I drain the oil and keep the filter ? how many time I need to change oil and filter after head gasket job ?