Upper LCD is Dark/Black

The Upper LCD screen is dark/black. I say Dark because if I have a powerful light shine in to it I can still see the game. This probably occurred due to rogue liquid (soda) finding it's way in to my console.

I would like to add this occurred after the top screen was flickering for a few minutes. Then the system shut off, and when I restarted it the top screen has been dark as it is now. Restarts don't change anything.

Everything else functions perfectly normal.

So I followed the Upper LCD Replacement guide, I haven't finished it yet though but everything is taken apart. My question is, should I replace the screen still as depicted in the guide? Or shouldn't there just be some grime (because soda) I can wipe/scrape away? I am incredibly, incredibly poor. I'm making less than my rent right now, which is why I ask. 10$ even is very important.

I found some grime I scraped away on the ribbon on step 18, dunno what that ribbon does though. Could be more elsewhere.

Guide I followed: Reemplazo de la pantalla LCD superior de Nintendo 3DS XL

From this question: How do I fix my black top screen on a 3ds xl?