Just undo stuff until it comes off. Cars are nothing but nuts and bolts so get stuck in. You don't need to read a book to tell you how to unscrew stuff do you?
Front bumper. Two big bolts that hold it onto the front panel and maybe a couple of screws either side of the wheel arches.
Spoiler. 2 pot rivets. Drill them out and put the hatch up, flip off the caps and unscrew the 4 bolts.
Seats. 4 bolts hold the subframes into the floor.
et al.
Good luck stripping it. If you're hoping to make money on it you'll find 90% of it is worthless crap. The only thing worth anything on an Si is the bumpers, seats and alloys if it has any.
