98 Astro awd shot head gasket
 

Its my dads van it has a little over 200,000 on it great body and interior he just bought it acouple weeks ago but the head gasket just went on it the other day blowing out loads of white smoke/burning the coolent.. Question is how hard is it to replace the head gasket on these vans? And also has anyone here ever tried using a product like steel seal or thermagasket? and if so how do they work or do they even work?