It CAN be edited with a plain text editor, but it's so easy to goof it up that I stopped advising people to do it that way. For instance, the end of a record is marked with a newline - but it's a unix newline, not a dos or windows newline. So 1) it doesn't start a newline in your editor, making it hard to see where one record stops and the next one starts, and 2) it doesn't even show (visible) in lots of fonts, on screen! When it does show, it's a square little box char.
To help with the passkey, you can break up the 32 characters, into groups of 5. That's a big help: 1a66f 200db etc., and then remove the spaces after you've double checked it.
Sorry about your lost wu.