Why would you need to mess with the shield?
http://mywebpages.comcast.net/xterra/tech/FrontBrakeJob.txt Quickie version: Remove wheel, remove lower slider pin bolt, swing caliper up/open around the other slider pin, remove old pads, push pistons back in to make room for new pads, insert new pads, swing caliper closed again, replace lower pin, replace wheel.