A heat gun or hair dryer works well. I like to use a razor blade to get the decal started and keep it going all in one piece. If your careful you wont mark/scratch anything and once onthe way dont even need to touch the body surface, just the decal.
Go to a local auto store like pepboys or murrays and they should have an eraser wheel its called shown here... http://www.handsontools.com/store/show_pro...product_id=2319 and all you have to do is make sure truck is clean and same with decal and put it in a drill and follow instructions.. completely safe for paint as well. My buddy has used this one here to remove the Daytona decal off of his ram, and we use them at work to remove the glue from the emblems of a car when that panel needs to be painted or whatever.