Car won't start, loud vibration, oil in sparkplug Wells, thermostat housing is bad

Hello, you are saying it has a thermostat housing that needs to be replaced, but hasn't been? Replace it! Oil in the spark plug wells likely means you need a new valve cover gasket and seals for the spark plug / coil holes. If there is oil saturated on the electrodes of the spark plugs, that is due to an internal engine valve train or base engine concern. When the vehicle has not been repaired or maintained as needed, it's very difficult to answer questions to try and figure out what one of many things would enable the vehicle to be driven further. It sounds like the vehicle needs multiple repairs of substance.