ProTip: Open the fill plug before opening the drain plug. It shouldn't be an issue on most bikes for an oil change, especially a brand new bike, but it's a good habit to get into. There's nothing worse than getting ready to finish up some work and refill the fluid, only to find out you can't actually open it up to put the new fluid in.
My 500's OEM filter was put on by a gorilla on steroids. I ended up driving a punch all the way through it and using that for leverage to get it to turn. I've heard similar stories from others. The original filter on a bike is somewhat likely to be on a lot tighter than it needs to be. Properly installed filters shouldn't be too hard to get off in the future.
If the HF303 fits the 400, there are a lot of compatible options - it's the same filter that the 500 uses.
http://www.ex-500.com/wiki/index.php...ross_Reference If there's extra room in front of the OEM filter (it looks like there is), you can buy a longer version (about 3.25" vs. 2.5") that will give you more filtering media and a tiny bit more oil capacity. Bike filters tend to be overpriced, so you can often find an "auto" version of the part with better quality for less money, and with better availability.