After you look under your trunk lid (remove carpet if you have it) and remove the plastic plugs, you'll see where you need to drill in comparison to the spoiler.
I think you'll make your decision fairly easily when the spoiler comes. I tiny bead of silicone caulking around each hole on the trunk lid will help give you some peace of mind during install, and for extra measure, do the same on the under-side before the nuts go on. Get that lid good and clean first.
A 14V Quality cordless drill should be enough. And I agree with center-punching and pilot-drill (small, perhaps 1/
to start with on each hole to prevent bit-wandering.
Put some paper or an old towel down in the trunk to catch the shavings, and maybe put a magnet under the trunk lid to keep them from getting between the trunk lid panels.