Once you have a derelict pinball machine the hard part is over. Now start taking the thing apart.
NOTE:Vintage pinball machines are collectors items. Make an effort to get parts into the hands of people working to restore these collectible machines. You won't be using all of the parts in this project so save the rest and don't send them to the dump! (Note that this machine was salvaged from the dump before you blast me for cannibalizing it in this way.)
Now you need to have the thing sit around your house long enough that your wife wants it gone so bad that she'll even help with the monotonous disassembly. That worked for me!
Remove the scoreboard area, the legs, and then get to removing the guts - well, most of them. You'll want to leave in the flippers, and any other items that project onto the play surface. If the mechanical system extends too far below the play surface you might want to fake it by cutting off a part and reattaching it later.