I just had a leak on my RT's LP tank fixed on Monday. The valve was leaking around the stem even when fully open and seated. It still had 4 gallons of LP in the tank which made a bit of a problem as no one could deal with it almost full like that. So, on a windy day, I drove it out in the middle of a field, disconnected both the coach and starting batties then let it drain out the tank vent. Took almost 8 hours, but was a pretty safe method and what the LP supplier had recommended. I had called several RV repair places and all of them recommended an LP supplier do the work. One repair shop gave me a specific place to do the work in Coleraine MN. I stopped at Range Bottlegas, walked in and had the first guy I saw come check it out. He opened the tank vent to make sure it was empty (still hissed a bit) then pulled the handle off the valve so he could see the core. Came back out with several repair kits and tools, pulled it apart, put the new parts in and had me drive over to the filling station. He put just enough of a charge in it to test all the fittings, regulator etc. After he confirmed there were now no leaks, he filled the tank completely.
Total cost? $18 Turns out the valve parts were only $6.50, the rest was for the LP. I gave him $30 and said keep it which he was a bit reluctant about even.
The whole deal took about 20 minutes. Hopefully you have similar luck in getting your LP problem dealt with. The short point of the story is that it may work out better to take it to an LP supply business.
Hope that helps!
-Mike & Heidi
97 RT 170P "Taj Ma Trek"