If you performed the mod or not, you need to reassemble the latch (see the photo for an example WITH the mod). Normally I would coat the parts an a little graphite. The problem in this case is that with such severe corrosion, I felt that graphite would not offer any protection from the process continuing. So I decided to use a thin coat of white lithium grease instead. I covered all the surfaces.
Now for the tricky part- getting the spring back in place.... and depending on your skill and dexterity, this might take quite a few attempts (it certainly doesn't help matters having the parts slippery with grease, either). The way I did it was to place one of the latches in the track first. Then inserted the spring, then placed the other latch where it would normally live, but on top of the spring. Then I used a small, flat-bladed screwdriver the pull the spring back while pressing lightly on the non-seated latch (it make take two or three pulls back). Once the spring is in place, the assembly is fairly stable and you can place the cover back on. Of course, nothing holds that cover on until you use the screws to put it back on the cap.
And here is a continuation of my warning from a while ago. With the latch off the cap, I tried turning the key to see how freely it moved. It wasn't that great, so I decided to spray in some graphite around the core from the top and work it in. That didn't help. So I decided to remove the rubber cup from the bottom of the cap to see what I could do. Eeek. All the little springs fell out and so did a tear-drop looking piece of plastic (some type of valve and a round screen). At least I could see the lock core and sprayed graphite around that, which did help some. It is obvious where the springs go. And the screen was easy. But I could not figure out which way the teardrop valve goes- one side was flat and had a hole, the other had no hole but little pips. The factory manual DOES NOT have *any* information about the tank cap at all. I took a guess that the pips went toward the screen and put it all back together.
So far so good. I needed to get gas right after all this, anyway. It was nice to be able to easily open it again. And even nicer to not having my key being held hostage while filling
I will report back on the long-term results of the "operation", especially to see how effective using white lithium is. But although I know it is going to corrode again, it is now pretty easy to fix (and I won't let it get this bad again).