You just need a large philips screwdriver to remove the door handle.

http://www.californiawesty.com/Vanagon_Key_Code/Vanagon_Key_Code.html

Once you get the key code (5 minutes work), you can order an entire
handle replacement that matches your keys from Steve's Lockshop in
Texas, then send him your old one after you swap it out.

http://www.steveslockshop.com/