Don't know how useful this will be, but I've had the pictures for a while and I thought I'd post it.
Before you begin, take out any disc that may be in the drive and remove the port cover on the back if it is still attached. Remove the six screws on the underside. They are just normal philips screws. Then carefully flip the system over and lift the TOP off. If you just pull the bottom off the disc reading thingy will flop around.
This is the inside of the PS1. Unplug the cables and simply lift the disc reader thingy off.
Remove the two screws on the power jack and disconnect the PSU if you haven't already. The PSU slides to the side and lifts out. Remove the two screws holding the controller/memory card unit in and lift it out.
Remove the three screws circled in black to free the shielding. The purple-circled screw doesn't have to be removed at this point but you will have to remove it later anyway so you might as well do so.
Take out all the screws holding the ports in. The board is now free of it's prison of metal and plastic. For those less poetic folks, it's now out of the case.
Like the N64 there is a plate underneath. Also like the N64 there is nothing holding it. Remove it if it makes you feel better.
All the parts of the PS1. The multimeter and battery-powered soldering iron are not part of the PS1.
I hope this was useful or at least something to read. Remember, this only applies to certain models of PS1.