You could drain the oil from the big flat head screw looking plug in the
bottom of the engine.  This is for the oil pressure relief valve plug and you
should be able to get almost all of the oil out this way.  If you are
suctioning out the oil I would recommend measuring what you sucked out, that
way you can see how much you are getting, etc.  Also putting the front of the
van up in the air and undoing the two nuts that hold the oil filler to the
base of the engine would be a third way to drain your oil.  Necessity is the
mother of invention!

Hope this helps.
Ken Wilford
John 3:16
www.vanagain.com
Phone: (856)-765-1583
Fax: (856)-327-2242