That's a really big job that is very difficult if the van isn't on a hoist. You'll need a transmission jack unless you can lift and balance 200 pounds with one hand while removing hard-to-reach bolts with the other hand.
You start by removing the drive shaft, cross member, cooler lines, shifter and kick down linkages, electrical connectors, and torque converter bolts. Remove the crankshaft position sensor from the top right rear of the engine so it doesn't get damaged. It needs a paper spacer to set the critical air gap when it's reinstalled. Support the transmission, then remove the bolts around the bell housing. Pull it back a few inches then let it down.