Sounds like you need one additional thing--a second opinion! The dash A/C was made by ACME, which is nolong in business [I think] but the parts they used seem to be pretty std for auto A/Cs. Depending on condition/what happened to the system, [usually a compressor failure or a hose leak] things like evap/dryer tanks and the expansion tube [not the tech name] are common replacements. If someone is saying "it all has to be replaced", I'd run.
2003 40' MDTS
Garden Ridge, Texas