There's a tar-like sealant that seals the lights into the boot. Just undo the nuts off the back of the lights, unplug the wiring harness, then if you can't push the lights out from inside the boot, make sure you have all the nuts off then sit in the boot and push them out with your feet.
It's easier to get the lights out if you park your car in the sun for an hour or so beforehand to heat up the sealant.
EDIT: I just remembered seeing a DIY article on boostcruising.com a while back, the guy left his lights in, masked all the bodywork around them and painted them with NightShades.