Cool... you'll love it.
Couple of things you might consider are the accessories you'll probably want for the mic itself. I'd suggest a pistol-grip shock cradle, fishpole boom, a foam windscreen for calm outdoor use, and for more windy outdoor usage you'll want a blimp cage with a fur windjammer (the classic "dead cat" or "monkey fur" mic cover). You can buy the mic itself and trick it out with all of the above in the $1500-$1600 neighborhood total.
Another thing to note: I'm betting that you will end up liking this mic so much that you prefer to use it in place of the stock on-camera mic in run-n-gun situations as well. It works well, just get a very short XLR mic cable and run it into one of the inputs on the camera rear. BUT... the diameter of the 416 is much smaller than the diameter of the stock Canon mic... so you will have to fabricate some kind of little sleeve if you wish it to fit snugly in the on-camera mic mount. This can be done easily by taking just a short length (say, 2") of appropriately-sized rubber hose and splitting it.
Another another thing to note: both Canon and Sennheiser will tell you that you should NOT connect the mic to the camera with the phantom power ON... that power should be OFF, then connect the mic, THEN turn the phantom on (the phantom for each channel is one of the two little switches above each of the XLR inputs). We try to be faithful to this practice, but it's actually very easy to forget and there have been several times that we have simply forgot and unhooked the mic with the power on, or connected it without checking to make sure that it was turned off first. I've never noticed any ill effects when we accidently did this, but it did make me nervous the first couple times. It's probably just a cautionary measure, but then again I don't like the idea of risking damage to a thousand dollar mic.
Good luck and happy recording!
T2
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Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com