In many recording programs (can't remember if there is one on FRAPS, but it should considering its capabilities) there's on option to split the video track and the audio track(s). I usually produce a video file with no audio, and 2 wavs, one with system sound (wich i never use anyway, i don't make game videos) and the other with voice or any other source i had.

This way you could remove noise from your voice and keep the game's audio clean.

Also, if your computer can't handle FRAPS well, check out other programs like Bandicam or Gamecam, stuff like that. FRAPS is PERFECT for recording but as Nugeddi said, it uses a lot of resources, while other programs are lighter. Personally i use Bandicam, the video quality is exactly the same, but it's lighter and encodes videos automatically (thus reducing the amount of GBs used)

You should try to sync all of them, because if you sync'ed up on the webcam and sound and not and the gameplay video and say Lets go over here or something and your standing still that would make any sense.

It doesn't really matter, as the voice needs to be sync'ed with BOTH the video and the facecam, while those 2 are impossible to be sync'ed without the voice. but i guess doing the facecam first is easier

I just use Xspit... FYI and BTW, my youtube channel is in action, but with only 2 videos, no subs, recent computer problems, and only 25 views I have a long way to go. Oh, well... I just need to fight on.