I replaced my 2009 MacBook Pro’s drive with an SSD. I used a tip from my scale modeling hobby when removing the screws: Back each screw out until you feel the click of the threads on the hole. Then put a piece of tape on the head and lift it out. The tape will hold the screw, preventing it from being lost to the carpet monster.
Oh, and the 3 long screws go the back right 3 holes.