well, for thos really wondering the exacts, this is how much it costs to do via radio shack:
i did it on my b15, and i just put it in. gotta reset the code, and then see what happens
. otherwise, i did it. vadium's instructions were quite easy to follow as well.
thing is, i diddnt use a cd case to make my 'box'
i used one of those plastic face scrubber/bar of soap plastic boxes. got it for a buck at the dollar store
. i did however use a think layer of duct tape, then packaging tape, then duct tape to waterproof it
. seemed to work fine when i put water on it.
i also found a great place to put it on the b15. right there where the sensor connector is originally located. put a couple zip ties in those holes, and you can secure it rather well.