Jonathan, did you buy a new camera with a black dot in the viewfinder, whatever the price ?
I have a stuck pixel in the rear color LCD of my 1Ds. I also have a dust speck between the focus screen and pentaprism, but it doesn't eat much, so I don't bother it. If I ever change the focus screeen, I may evict it, but it really isn't worth the hassle. It makes no sense for me to give up the use of an income-producing tool for a period of days or weeks unless the "problem" affects the operation of the camera or my ability to use it to capture great images, or compromises the quality of the results.
Dust happens; either learn how to deal with it or live with it. Expecting Canon to exchange your camera over a dust speck in the viewfinder is simply ridiculous.