The drain plug will leak, so best seal it up. Be aware that silicone may not stick well to the plastic, so a big gob of silicone is not the best way to go. Best is to take off the rubber valve at the end, find something which fits the hole exactly, cap the end of the hole, and refit the rubber valve, to hold it all in, with plenty of silicone to make sure it seals.
The plastic rivets still in the wing should have been removed when you took the wing liner off
They generally come out easily with a screwdriver and fine-nosed pliers - remove the centre stopper first, then the outer section comes out easily. If you've bust most of them you'll need some new ones from your local dealer, they're not expensive.
If you're doing serious wading, you should also use silicone sealant to seal all the joints in your air hoses between the air box and the engine. I did this and the engine ran fine under 2-3' of water.
HTH
David
