The good thing is, so am I.
From posts, youtube, and websites, the yellow stains are usually present- there is a small amount of yellow powder-like substance, but I originally thought it was pollen. It was on the accordion-like sheathing over the copper gas line. Should I assume it had a small leak and it's shot?
If so, has anyone out there worked with this guy?
https://rvcoolingunit.com/Default.aspx
he seems reputable, and a new Amish for $655. We only run 3-4 weekends a year, and two weeks in July, so it would be more economical to get the rebuilt one to me- now we're looking at about 424 with the 'core'