John, I can sympathize with your problems and though you certainly are better off dealing with both a known and licensed business, still as unfortunate as it is, that alone doesn't mean you will get anyone that knows anything.

I own a service business (refrigeration) and I see people in supply houses that work for major contractors asking questions that scare me. Things that a first year apprentice should know.

A good friend of mine who manages one of these supply houses once hired me to come in and look at 30 or so failed compressors that were returned by one company. I found that 27 of the 30 had absolutely no faults.
Now imagine you as the property owner paying for something you didn't need.
Yes, it pays to do your homework, not get the guy that works out of the trunk of his car.
Pay the extra money for in the long run you will find cheap is expensive.

I have been in this business for 40 years. I think I have a good reputation and while I can't be all things to all people as customers sometimes leave to go elsewhere, the majority come back after they have had their fingers burnt.

I always tell them. If I do something wrong, TELL ME. If I do something right, tell everyones.

BTW, Tuna fish is on sale here next week LOL how are prices in Florida