Thought I might add, there are variations in keys... hinges are on the top and bottom left hand side for function keys, and caps lock, apple, shift and tab are slightly different, but nothing too difficult.
When putting keys back on, carefully remove the plastic piece from the keys (one end snaps, the other slides in sideways), and attach to the keyboard. Now you can slide one end of the key in and snap it into place. (for most keys, slide bottom down, and top in)