Hi there, I believe the Blade drive SSD (Apple Proprietary) is located on the back of the logic board, if your model came with a Fusion Drive. You can just replace the regular 2.5" rotational HD with a 2.5" SSD, the Blade drive replacement will be very expensive. Before you do so, make sure to backup your unit, if you break the fusion link you will lose all data. Also if you are doing the upgrade yourself, be very careful when removed the Display the glass and the LCD are fused, and if you are not careful you will crack the glass, which means a complete the LCD+Glass replacement.
Take your MacBook in for water cleaning. It could be a number of things. The damage only gets worse over time if the laptop is not properly cleaned. With MacBook airs l, I have seen the keyboard stop working followed by the MagSafe board.
Insert the new card into the phone and format it for use in the phone. Connect your old card to a computer using a memory card reader. Then connect your phone to the computer and manually transfer the files over. Data files will move no problem (pictures, movies etc.) app folders probably won't work. There may be software out there that will let you clone the old card to your new card. That might also be an option.
There are SSD adapters that allow you to use standard M.2 NGFF PCI-E. I have not used one but that could be an option. Saw a few on amazon. https://www.amazon.com/gp/aw/d/B0173ODBC...-4&pi=AC_SX236_SY340_QL65&keywords=macboo...
One the first picture of the fan, showing the black screw. The spring goes in under the screw (i.e. The screw goes threw the middle of the spring) to create tension and push the fan down. Hope that helps!!
There is a sensor inside the SD card slot. Which detects the card lock on the side of the card. Something may be blocking the sensor, it's dirty or it's damaged. I was googling and it appears others have had the same problem even after replacing the card slot internally