I'm assuming you bought the OEM spoiler. If so, then here are a few hints that I learned from my installation (which was posted here:
http://www.greenhybrid.com/discuss/f...rear-end-9741/ ):
1) To remove the clips, use two flat-head screwdrivers and insert one from either side of the clip, then just pry upwards and they will pop out very easily.
2) You probably do not need to drill the two large access holes in the bottom of the trunk lid as the instructions suggest. The instructions assume that you have a 1-piece tool that needs to access the two mounting bolts. But using my rachet set, I was able to feed the bit thru one of the the larger existing holes, then stick the ratchet handle thru the existing smaller hole, and put together the ratchet "on the other side". This description sounds weird, but once you see what you need to do, then it will make sense.
3) As with any work, measure twice and cut/drill once!
4) Drill slowly. Due to the rounded shape of the trunk lid, the drill bit might walk (which it did on me) and you end up with a scratch. I punched using the template, then removed the template and drilled a small starter hole at each location, then drilled the final hole.
5) Make sure to coat the drilled hole with rustproof paint so it doesn't rust.
This project took me about 3hrs but only because I didn't have the correct size drill bits and had to make a visit to the local hardware store. You should be able to complete this within 2hrs if you have the right tools.
Good luck!