It's not working for me either, even tried creating a new account which displayed "Invalid Username" once again... and then I created another one to make sure I didn't derp something :confused:
Yep, you just have to point the strings to the right locations, and make sure that the sql tables exists.
It only takes about 10 minutes if you know php, or just only know how to read it
Yeah $600 is "cheap" (if you plan to make money off it), there was a botnet (Zeus) that was going for $3k that used this method last year. And hackers* even pay $10k-50k for the latest security exploits
Hacking is an expensive hobby