First of all, if you're not well experienced with auto AC, take it to a
shop.  It may save you some headaches.  But, if you feel competent and want
to try, here goes....

I show that the freon capacity of the Vanagon Syncro is 51oz.  As long as
there is still pressure in the system, you should be ok with just a
recharge.  If the system went totally empty, you will then need to change
the dryer, evacuate the system, and then recharge.

If you have a set of gauges, put them on and see if you have pressure.  If
it's over say 20lbs of pressure, you can assume that you got it closed up
before and air or humidity got in- so, just recharge it.  Charge until the
high side reads a little over 2 times the ambient temperature.  Duct
temperature should be 35 to 45 degrees.

If you don't have pressure, remove the dryer and replace it with a new one.
Don't leave the new dryer open long and hook up a vacuum pump immediately
after the dryer is in and pump it down to 29hg and continue to pump it down
for 1-2 hours.  Then recharge the system with 51oz of freon.  Also,
depending on how where you opened the system and how much leaked out, you
may be a little low on refrigerant oil.  You're the only one who knows how
much oil blew out with the freon, make a decision.  To do it perfectly,
after you remove the dryer, drain the remaining oil out of the compressor,
purge the system, add the factory specified amount of oil, then install the
new dryer, vacuum  freon etc...  Vacuum pumps are available from Autozone as
a part of their loan a tool program.

Good Luck, glad no one got hurt.

Dave