When I got to this step I realized the screw was stripped. I'm unsure if it was stripped by my efforts -- I used the prescribed P5 screwdriver that was also used for the other screws, and the screwdriver still works when putting the lid back on.
So to extract the stripped screw in Step 5 I've ordered iFixit's Precision Screw Extractor Set.
Now I'm wondering if I also need to find a replacement screw since I probably won't be able to use the stripped one again after it's been extracted? The screw is called: 3.1 mm T5 Torx screw as per this guide .. the best I can find on eBay are screws called: 1,4 X 3,1 mm Torx T5 or 1,5 X 3,1 mm Torx T5 ... will one of these work? Would I be able to just go to a hardware store and find the proper screw or is it a specialty item?