For those who are stuck or new to ciphers check out some of this wiki article:http://en.wikipedia.org/wiki/Topics_in_cryptography
Since you've found the key already you should be able to rule it down to a few different cipher types. Read up on them, and one you know how they work you can easily pick the one you need.
You basically have it done, (stego part) you just need to decipher it
Big hint: its not too common. (Basically giving away alot of hints since this is a stego challenge and not an encryption challenge.) The decoded pass is not a real word.
BTW is there a way to see how many people completed this challenge? I remember you could about 2 years ago, but I don't see the page