replacing "bad" audio track with "good" audio track for video file

i have a project going, and i am having some trouble. i have Final Cut Pro, Final Cut Express, MPEG Streamclip, and many other video editing softwares. i have managed to remove the "bad" audio from the video, and have the "good" audio" i want to replace it with handy.

after i get the 2 audio sources synced up where the "good" audio track is ready to be attached to the video, where do i go from there? by reading this im sure you can tell i run ,

is there an application that will do it for me? i am looking for the best program to attach the "good" audio track, and keep the audio synced with the video.

please, any suggestions? i have a career i can make out of this. all help appreciated. thanks

 

What format is the video source and the good audio?

 

video mp4, and audio vbr mp3

 

any suggestions on conversions of either the video or audio? the video quality (MP4) is the master format, the audio is the best format i could find for the source. what would you do?

 

If the audio is synced with the video, try Yamb and combine your video and audio that you want and create a new mp4.
You want to convert to what format? Why?

 

im sorry for the confusion, i do not want to convert to another format unless i have to.

all the programs everyone is listing for me are for PC, i run . any suggestions for a mac user?

 

Sorry I missed the part about working on a Mac.

Try this software, it suppose to be able to convert, mux/demux, split...,but I am not sure if it is free;might just have a trial period, however, if you're "making a career", might be worth investing in:

http://ffmpegx.com/index.html

This one is free:

http://mac.softpedia.com/get/Video/PEnGUIn-TooKit.shtml

or this:

http://www.macupdate.com/info.php/id/17483/quicktime-muxer-flattener