Any advice in general of things I might try myself before I lay out money for a new coil?
I apologize in advance for my prejudice... I expect all the HVAC guys here are going to weigh in tell me what a jerk I am for even considering repairing this myself because it is technologically beyond the abilities of a DIYer and how HVAC guys are all honest and of impeccable credentials and ad museum. Unfortunately, in my experience with the industry-at least locally-it is about as open and honest as the Sopranos. I am very distrusting of the techs and "certified" HVAC people in my area. "Jethro", the original "certified" HVAC installer stiffed me on the initial installation doing about 75% of the work for 100% of the money and then disappearing; he lost or parlayed the unit's warranty info and in the end I had to hire another installer to finish and correct his work. This is the rule, not the exception for (native) North GA residential building "experts." The original installer declared bankruptcy and retired after being tragically struck in the head by his meth pipe. I am convinced that even though HVAC service and repair seems to be mystified by the industry as something akin to rocket science, that if Jethro and his ilk can become "certified" HVAC installers for a company like Trane that I ought to be able to figure this out myself.
So ... any actual DIY advice would be appreciated.