Oh my, are you in a world of hurt!
My question to you would be: why? Is there a lens that Nikon makes that you simply can't get from Canon? That 200-400 perhaps? Or is there a box full of F-mounts next to you that you simply want to use?
The reason I'm asking this question is that more often than not people think that having the ability to mount their old lenses on their new cameras is as easy as buying an adaptor, and shooting away.
There are several reasons that people get these adaptors. The first are the image purists. They believe full-heartedly that that Zeiss Distagon 21mm is the best there is in terms of optical resolution (which it is), and that they must use it to get the best images, and if that means stop-down metering and manual focusing, along with replacing their focusing screens and shaving their mirrors, then so be it. The other group, which might be your case, is those that have (or inherited) a bunch of lenses from another mount, and simply want to use them, not necessarily understanding what that entails.
Here's the deal- a mount adaptor is OK- i.e. it works. They do not convert one F lens to an EF lens though. You lose the ability to autofocus (more often than not), and you cannot use the metering inside the camera. Unless the Nikon lenses you have are manual (i.e. giving you the ability to change your aperture manually), you might as well not bother. Metering is another problem, and you will have to learn stop-down metering. What that means is you need to manually focus on an object at the lens's largest aperture, meter, then go to the aperture you need and adjust your shutter speed from what you got from your original metering. Last, but not least, there are some lenses that will simply not work on a canon mount (as the mirror will hit their back), and you might need to shave your mirror.
If you have the Nikon glass already, wait and get another hundred dollars or so, and get a D50 (or D40, if your lenses have motors). If you're one of those purists, trust me- today I tested a Contax 28mm f/2.8 (Zeiss) along with my 24-70L on my 5D side by side. There was no discernable image differences. Having the ability to meter properly, and autofocus if I need it, is enough to be satisfied with having that Ferrari over the Bugatti.