Schrader valve?

OUr 1997 Chevy Astro. Vin w. Is having problems, it will drive normal for a little while then it looses power, starts to die, the oil pressure gauge drops and then it dies, some times it restarts just fine and runs normal, sometime when it restarts its all we can do to get it to go over 20 miles an hour. We are trying to replace the fuel filter, but can not find the Schrader valve to release the fuel pressure first. Please help us out here, my husband is on leave from the Army and if we can get this fixed today he will be in a lot of trouble getting bcak late.