Transposing audio is not easy. Unless I'm missing something in that OP.....
You would need to go back to BB and change the key there, then you can render a new audio track in the correct key. Or record it again on the live instrument.... those really are the best ways.
Most key conversion programs which change the note pitch are problematic.... even the best which I consider to be Melodyne, will leave artifacts that are not desirable in the final mix especially with large jumps or sloppy editing. The bigger the key change the more likely you are to encounter artifacts from the conversion process. Half steps or less are generally OK.... but from C to E is 2 1/2 whole steps.....that is a huge jump to try to transpose flawlessly.
I have found a program...which I do not own..... called Key Changer
http://www.songgalaxy.com/software.php I have tried the demo version and it works OK but has artifacts..... but you have to convert to MP3 which is self defeating with the music we record.... we want to work with waves and not mp3 for quality reasons.