Ahh well I'm in Columbus, Ohio--technically the midwest----so can't really recommend anyone your way. I'm still fairly certain a good independent A/C dedicated shop or over all great mechanic has some experience in this and wouldn't require a lot of experimentation at your expense. Maybe see if there are shops dedicated to servicing campers/RV's or conversion vans in general---not the stealerships though.
When I helped my friend he co-owned a van conversion and service shop-----he had a lot of experience in this very thing.
Hoping the best for you!
I ran through Columbus yesterday morning on my way back to NY from Iowa. Had breakfast at Waffle House on Roberts Street. I was surprised how nice and clean the city was. What also surprised me driving from Columbus to Akron is that Chevy passenger vans outnumbered Ford Econolines 10 to 1. Here on the tri-state area (NY-CT-NJ) that ratio is about 2 to 1 for Ford. I just count them as a way to spend my time while driving.