You have to remove the dash to get to the blower (guy at dealership is used
to dealing with Jettas not Vanagons).  To removed those two funky bolts just
use a pair of good "Vise Grips" TM on them and they will come right out (not
that tight to begin with).  You can get new from the dealer.  You will then
need to pull the blower housing out so you can get to all of the little
plastic tabs that are holding it together and cut them off with either a
dremel or a pair of cutting pliers.  Now remove all of the control cables
going to the box and remember where they were so you can replace them later.  
You don't need to unhook the heater core, just loosen the two phillips head
screws in the top of the blower housing and remove the top.  I have new
Blower fans if you need them for $75 each (new, VW).  When you go to put
everything back together you are going to need 10 little clips that you could
buy from the dealer, but I also stock these.  They go for $2.20 for all 10.  
I would also use a little silicon to seal the box back together.  That is it.
 I hope this helps you.

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