Blur face in 28minute 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 included a 20 second sample of the video in WMV format so you can see what it is like. I’ll pay an additional fee if you can change the voice as well.