Don't know if it's attached exactly the same as mine, (99 Cobra) but you should be able to remove the inner cover on the trunk lid and there should be bolts under it holding the spoiler on. They may have used a double sided adhesive between the spoiler and the body to help hold it on. If anyone has done the '03-'04's and the're different, please chime in.
Why would you want to take it off? I would recommend doing the minimal body work on the holes etc and not just putting plugs in them. That looks rigged.