I am a Newbie at all of this but when I needed help with my propane tank 
we just took the whole thing off and took it to a propane fill station 
that does the whole nine yards, installs tanks, refills, repairs ets., 
not just filling tanks like for your gas grill.  They put a new bleeder 
(spitter valve as they called it) and a new fill valve on it, pressure 
checked it and handed it back to me.  I think the whole think cost us 
about $30.00 but it was worth it.  They made us sand and paint the tank 
first because in this state (MA) they can't touch it if it has visible 
rust. Once installed back under the camper they filled it.  They 
explained that because of the type of tank, they weren't allowed to fill 
it until it was permenently installed. For the lack of headaches, I would 
say - have it done for you, then you can be sure it's right.
Good Luck, Wendy
'85 Wensy  "S-Cape"