Um, this guide should include steps for applying thermal paste, including instructions to clean the mating surfaces, and pictures showing how much thermal paste to use.
The SSDs are hardware-encrypted by the T2. If the drive(s) are removed, the data is unreadable.
The battery from a supplier on eBay cost about $5. The repair took <10 minutes to complete.
One note of caution: if you trim the ears for easier replacement in the future, be advised that the tray will have a slight tendency to pop out, about 1mm from the back of the keyboard. You could use a piece of tape to hold it in, but the tray will not slide or fall out very easily on its own.
I was able to perform this step on my first repair attempt. Here's a tip: the rounded part of the headphone cable is very stiff and "spring" like. Just take a very thin Philips (#000) screwdriver and lay it down on the cable diagonally, pointing almost directly towards the screw. Push gently down on the cable and it will cave in somewhat. This is fine. Then you can go straight in at the screw and turn it out.
The rubber bumper has a groove in it, which rides a notch along the top edge of the logic board. Its purpose is to ease pressure between the top of the phone and the board. If you look at the top of the frame, there is a little horizontal ridge about 0.8cm (3/8") long which is just the right width of the rubber bumper.