First of all, we need to know if you understand how the oil filter is to be installed - it isnt hard, but it also isnt as obvious as some might think. Also, have you noticed the oil pressure warning light (red light in center of dash, but do not confuse with the GEN red light) come on when the engine is running?
I would get an oil filter from a dealer with the entire `kit` of bits - it should come with the oil filter, a paper gasket, a large o-ring (used to be white, some might be black in color now), and a circular metal `shim`.
When you take the 3 bolts off the oil filer cover, some oil will come out, but not all of it. Still, you may as well drain the engine oil first and plan on replacing that as well. When you remove the oil filter cover, it will likely have large o-ring stuck on the inside of it. Inspect this for cuts, nicks, gouges, etc. You will be replacing this with the new one from the kit, but if that o-ring is compromised, it can cause the leaks, and it can also cause catastrophic drop in oil pressure which can damage the engine in short order - this is why it is called the $2000 o-ring. You can google it for more info if needed.
The next thing in the housing should be a thin circular metal shim, with the oil filter probably sticking to it. This shim is also a very critical part of the puzzle, and if it is damaged it must be replaced with one from the oil filter kit. You will also notice that the shim is just stamped out of thin metal, so one side may have some sharp ridges on the edge - these ridges should be placed INWARD toward the filter and AWAY from the delicate, $2000 o ring
Anyhow, remove the oil filter and examine it for signs of being crushed/flattened - this can be a sign of excessive pressure - or just a crappy quality filter. Many of us use the hinged-filter (looks like 2 short filers with a flexible hinge bit inthe middle) as these are sturdier and less prone to flattening, but a quality single straight tube filter should also be OK.
After removal of the oil filter, look down into the oil filter housing - it is often called the cannister - and at the `bottom` - actually the furthest in wall, you should seewhat looks like a small ball bearing showing - this is the pressure relief bypass valve which takes over if the filter cannot flow oil back into the engine. Just take a long screwdriver and push inward on that ball bearing thing a bit to see that it moves inward and springs back into position properly.
Around the outside of the circular oil filter canister, but under the outer edge of the oil filter cover you removed, is where the paper gasket goes - if it is needed. If your bike has one on it, the paper gasket it probably cemented to the outside of the engine case at this point. The paper gasket is used to control the amount of compression of that big o-ring. The paper gasket itself doesnt really seal in any oil. The o-ring is supposed to be compressed by between 15%-25% of its thickness, making it appear slightly squared off in cross section instead of round when it is removed. We measure the depth of the oil filter housing `lip` just inside the engine case to determine whether to use the paper gasket, or not, or sometimes a couple gaskets, to achieve the proper amount of compression. We can help you with that bit in a followup post on this thread.
For starters, I would begin by getting the aforementioned oil filter kit as you will need that before you dive in there.
