Actually, it will depend on what spoiler you have. If you have the factory wrap around wing, 99+ style then you will not get water in the holes. If you have the factory pedistool (sp) wing then the mounting holes are on the inside of the seal and water will come into your trunk.
Since yours is an 02, I believe it comes with the latter of the two and will leak water. The best way to check however is to just take it off and see if you see trunk or not, (assuming you have nothing covering the holes from the underside). If you do see trunk, get some silicone and bead it around the plugs until you can buy a new trunk or have the holes properly filled.