Don, so that you don't feel too bad.... A public confession of my wiring ineptitude.
I was very happy to find this mod. Sounded simple enough, great directions and photos provided, and I routinely wire-up all my stereo installations in my house and friend's houses.
So I ordered the caps, opened the panel, found the wires, snipped, and... yikes, that's a tiny wire! That's really hard to strip. And there's very little slack / play in the harness, if you should make a mistake. (Never happen to me, of course

)
And how the heck to connect that tiny wire to the cap? Bought a bunch o' wire nuts, and none of the worked. Didn't have soldering iron -- haven't used one in so many years I'd prolly burn a hole in the door
Then I noticed that I barely had enough speaker wire "play" left to reconnect. I joined up with a wire nut, held my breath, and turned on the stereo...it worked as before I started this little project.
So, I'm at square 1.