Just in case anyone needs to replace a service valve and is searching through the archives, here's a link to an outfit that sells one for about $20.

http://www.protanksupply.com/valvesdetail.asp?sku=6012

I can also say after completely rejuvenating my propane tank, replacing fill valve's bleeder valve, and now the service valve (regulator is still original) I would buy a new tank without a second thought if I had this to do over again. I think this is one case ( at least for me)  that turned out to be way more effort than what I saved by doing things myself. I'm thinking I still may have some issues with the "extend-a-stay I installed. Gettting a leak free set up is very challenging. I ended up using red loctite on a number of the fittings, simply because it's very easy to break the seal on a fitting putting this together with the standard Teflon paste. I do like the extend a stay, but again, it's challenging to install. It's really not designed for a vanagon.

I'm now in the process of emptying my tank once again, undoing all the fittings so that I can replace the service valve. It's been leaking on an off for a week now.

Troy