Use hot water or a hair drier to remove the rear, some dental floss will be good to help remove it since you wont really be able to get a grip on it to pull it off. And the front i think is held on by clips.
you can watch how to do it on youtube, i think you just need to buy some glue from halfords to stick the new emblem on the back. make sure you mark it out properly though with masking tape.