Jeff
I've never tried to change my PDC sensors from the outside, but to be honest it's not that difficult to remove the back bumper. 2 screws and 2 bolts hold it in place. See
http://www.xoutpost.com/showarticle-91.html for an idea of how to remove it.
It's helpful to have 2 people doing this, as it is quite bulky.
:xoutpost: