Before you tow it, drain the oil and filter and then clean all the plugs off with a spark plug cleaner.. it's a small sand blaster and then install the plugs and see what happens
We get this all the time with postal explorers and sometimes even brand new cars. Once the crankcase get fuel contamination the fuel ratio will become to rich due to the PCV filling the intake with vapors from the crankcase.. this will foul the plugs instantly
But since it's a 96 windstar you might have a blown headgasket but first you need to find out if it's something simple before you tow it and they tell you it's a headgasket, when it might only be simply flooded.
BTW the fuel also washes down the rings , this will give you a very low compression reading since the rings won't seal..
I would drop a tiny tiny bit of oil into each hole when you put the plugs in and if you can crank it with the fuel pump disabled to try to coat the walls again with oil