Great write-up, Otto, many thanks!
I do have one question regarding the following pic - I thought #4 was farthest aft on pax (right) side? This one looks like #5 to me...am I all hosed up? (it matters, as I have a P0304 to investigate and thought I'd swap COP's between #3 and #4 and see if the miss migrates from 4 ot 3 - will accomplish plug change with another study of your post once I have that sorted)
Here is what the socket on #4 looks like. Loosen and remove the sparkplug.