RE: Discover II 2000 - P0307 Cylinder 7 Misfire Detected
Before you jump the gun, how many miles on the truck, when was it last tuned and were the plug wires replaced?
The gas did not cause the misfire, and as Spike has mentioned you MAY need plug wires.
How mechanical is your husband?
If you buy wires, order a set of 8 mm Magnacor wires from Cerrones, 650-365-4145, do not order the intake manifold gasket.