Hi, you dont say what engine it is, but if its a 1.8, 2.0L or crossflow 1.6, There is a Bakelite sort of flange which bolts to the side of the head with two bolts, attatched is a coolant hose, there is also one on the front of the head, these tend to crack and leak. Replacement items are cheap and takes little time to change.
As for the fuel, is it a burnt exhaust fume sort of smell or is it petrol vapour? If the manifold is leaking, it will certainly smell, Not uncommon to get cracks in the manifold, leaking crank case vent pipes will also cause a bad smell.