Raise the van and suport the rear axle on jack stands. Soak the three j-hook bolts with a good penitrating oil such as WD-40 or your favorite type. Now unhook the battery. Syphone out the gas if possible. Have a good jack and/or helper so once the tank is loosened you can carefully drop it down.
Disconnect the filler tube from the gas door, three screw/bolts. Unhook the filler vent line as well, part of that line goes over a support that is under there.
There is a vent line from the charcoal canister just forward of the tank you should loosen to help get the tank down.
Position the jack or have your helper ready after you lossen the j-hook bolts and have the nuts just about ready to be removed. You can either loosen them just enough to lift the j-hooks out of their sockets or take the nuts completely off. Be sure either way that you are ready for the weight of the tank.
Now lower the tank some so that you can unhook the electrical connector and the fuel line.
Once that is done double check for any missed connections then drop the tank and slide it out from under the van.
Remove the top with a special tool that you can rent from O'Reilly Auto parts store and take the lock ring off of the tank. Then lift out the fuel pump assembly.
Haven't done one of the tanks that is mounted mid way (mine are all too old) but only rear ones. I make 3/8" threaded rod extensions, then you can let the tank down on the "J" bolts enough to see what is going on on top of the tank. There is a capped connection there that will allow you to siphon out the remaining gas, you probably won't see it until you have the tank off, but it is there. If you have trouble disconnecting the electricals, the cable has a connector ahead on the otherside of the crossmember which is easy to disconnect (rear tanks). I find if you extend the "J" hooks you can do it alone. One final tip.... make a super long socket for those nuts, weld a 6" piece of 1/2" pipe to an old socket and top it off with a 1/2" nut, then you can use a 3/4" deep socket to gain even more depth if you still need it.