Rain will most likely get in it if you take the spoiler off and dont replace it or fill the holes. I just swapped spoilers on my 03 mustang and left the spoiler off while I was painting the new one (Big mistake, it rained while the paint was drying and got water in my trunk)
You can probably find some plastic caps, or screws with a flat head to fill the holes temporarily just to see how you like it.
As for removal, I would think the bolts would be the type that have two types of tread, one side bolts into the spoiler, the other side, with different tread, has a nut in the trunk. If you look in the trunk you should be able to locate the nuts, probably 4 atleast.
Good luck, and keep us updated.
