Why not just wire in a simple kill switch for the engine of your van.  That
way they can't steal it.  Just get a small automotive switch from Radio Shack
and some wire.  Run the wire down to the fuel pump.  Attach one of the leads
to the body of the van and the other to the negative terminal on the pump.
Now you have a simple kill switch.  Put the switch under your driver's seat
and then you can easily flip it off when you come home for the night.  Crooks
would probably never think of a kill switch that would allow you to crank the
car over, but not allow the van to start and they won't know where the switch
is so they will give up trying to start the van and go away to bother someone
else.

Way cheaper than getting all the keys redone (which you can still do anyway
for piece of mind later) and something you can do right now, instead of
waiting.

Thanks,
Ken Wilford
Van-Again
John 3:16
http://www.vanagain.com
Office: (856)-765-1583
Fax: (856)-327-2242