As I read, the end of the "Preliminary Expectoration" is trying to avoid a sort of trivialization of what Abraham does. In particular, it's a trivialization that we can call "Hegelian" if we want that reduces what is happening to how it ends. Maybe the best way to illustrate this is like this.
Q: What happened to Abraham with that whole sacrifice Isaac thing?
A: tl;dr Abraham kills a goat instead and God is happy.
The point here which ties into a major point of the text is that Abraham actually has to be willing to kill Isaac and it has to be something he genuinely deals with. He actually has to have this resolve not just for a moment but as the quote explains -- for three days while riding on a donkey up a mountain.
The "don't call it a trial/ordeal" bit is hard to follow, because one natural meaning of this is to describe something difficult, but I think in English just as in Danish, it can also be trivialized, "you wouldn't believe the ordeal I went through today." -- "I had to wait for hours to get the new CD."
One thing that might make that bit harder to follow in just reading the text by itself is that you need to keep in mind an image Kierkegaard used much earlier which is the image of the church sermon on Abraham. Kierkegaard looks at from several sides how the sermon is not being taken seriously.
Earlier in the expectoration, he points out the preacher who does not take it seriously. Here near the end of expectoration, he points out how the listener who skips all of the details is not taking it seriously and contrasts that with the "insomniac" who stays awake through the sermon and ponders what Abraham is doing in all seriousness.
All of this is again to emphasize that the author does not think the story of Abraham can be sold lightly or cheaply -- or brought under a number of more palatable descriptions. ("But to sell a cheap edition of Abraham and yet forbid everyone to do likewise is ludicrous" Hong 53 / Men vil man afhænde en Godtkjøbs-Udgave af Abraham, og dog formene Enhver at gjøre ligesaa, da er det latterligt. SKS 4.147)
tl;dr - de Silentio wants us to pay very close attention to what he thinks Abraham is doing when he's willing to sacrifice Isaac and not to skip over the reality of the struggle or what it means for Abraham to do what God commands -- even when the command is to murder the son born of God's promise to him.