Blur face in 29 minute video

I have a 29 minute video in which I need to “blur” or “black out” the head of the person talking in it. (I'm expecting a price of $10-$40, unless someone tells me why this is unreasonable) The video file is 6 Gigs and is in AVI format. I will be posting it on the internet for web viewing when finished, so if the quality is reduced that is OK, but I would prefer you return it to me in the same quality as it is now (720 X 480, 29.97fsp). I have exported and attached a 20 second sample of the video in WMV format so you can see what it is like. The scene does change several times in the video. I’ll pay an additional fee if you can change the voice as well.