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!