Repairing my sister's old 3DS (Part 1/2)

Recently, I rediscovered my sister's old original 3DS that had sat unused for many, many years, as it had died sometime around 2017/2018 overnight for seemingly no reason. It would turn on, before making a pop sound almost immediately afterwards and turning off. After all these years, I finally have the tools, and time (although not the skills or parts) to repair it, but after about 30 minutes of following an iFixit guide, I managed to have the 3DS disassembled for me to do some simple, quick fixes. I used isopropyl alcohol to clean the sockets and ribbon cables responsible for the speaker assembly and display. However, this provided no resolution. Since I'm pretty inexperienced with any DS repair (I haven't ever tried to repair a DS in my life), and I had managed to tear the top display ribbon cable while extracting the board, I decided that buying a working 3DS entirely and just swapping the board would be the best course of action to fix her 3DS as I didn't want to end up permanently damaging the console's board and render it irrepairable, or to have to deal with opening the top display and doing a ton of extra stuff. The donor will be a 3DS with a broken game card slot (I'm doing a board transplant, and the card slot on my sister's 3DS definitely worked before the console died!) that I found on eBay for £69.99 and will be arriving in around 2-4 days, ready for the repairs. Hopefully, everything goes well!