First of all, the problem could be something as simple as a weak battery. Modern electronic ignitions require a LOT of electrical power to start and run. Just because the engine will 'crank' does not necessarily mean that the ignition system has enough power to fire the sparkplugs. If you have a known-good battery from another car that will fit in your battery box, I'd try swapping batteries first.
Past that, I'd guess that the two most likely components to fail would be the coil or the crankshaft position sensor. An OBD II scan would probably give you the answer. Otherwise, I'd recommend having the van towed to the dealer or a reputable technician and have the ignition system tested instead of spending more money replacing parts that may or may not be working.
There's one other common problem that could cause the van not to start - a broken or damaged timing belt. However, this problem doesn't usually cause the spark plugs not to fire...
I do wish you good luck!
Dave B.