Replace wiring harness: Priceless! (Or very nearly so)
After replacing the original starter for a new one in the hopes that it resolve the "One click, no start" problem (and having that hope crushed mercilessly), and having temporarily resolved it by cleaning as much of the corrosion on the positive battery cable as possible, I took the vehicle into a local trusted shop to see what to do about the cable.
Because the corrosion "leached" down past the splice on the cable that attaches to the battery, I got two estimates. The first, which replaces the harness with a brand new one, was for just over $1,900; the harness itself was $1,700!!! The second estimate was to fabricate a new cable to extend from the battery into the harness, and that came in at just over $400; the owner called this a "permanent fix". He said that once he pulled the cable off of the harness, he would assess whether corrosion had gotten into the harness itself and call before doing anything else.
When I asked whether pulling a harness from a junkyard was an option, he said there was too much risk that I'd inherit the same problem; he estimated that costs to buy it from the junkyard and have him install it would be in the same ballpark as the $400 estimate to have him fabricate a cable and install that. Also, he wouldn't warranty any work done with the junkyard harness, but his cable fabrication would be covered for 12 months/12,000 miles.
I'm leaning towards the cable fabrication.
Any advice, comments, miracle salves would be greatly appreciated!