I don't tember seeing a gasket on the drain plug so I think you're okay there, just clean the surface of debris to ensure a good seal.
The genuine Yamaha part number is 5GH-13440-20 and that was the identical one that was originally on the bike. The 13440 part looks right and I do know that the I had 00 instead of 10 at the end of the part number for the first couple of changes then it was 20. They told me the 00's were old stock. I usually buy the filters a couple at a time and the last time I bought some was August of 2008 which was the 5GH-13440-20's.