just like a car, replace the oil filter. They are pretty cheap. Word of advise on the oil filter is buy the special wrench that goes into a socket wrench. I tried to use a wregular strap wrench and it wouldnt budge, not enough room in there. Yamaha actually didnt have any when I went to buy it so I ended up putting a screwdriver through the filter and turing it that way but what a mess it made. I already had drained the oil and wasnt about to put new oil in there for my ride the next day, so I had to do it, but buy the wrench!!!!
As for the oil, Yamalube or any other ATV oil. The important thing it that it is not labeled ENERGY CONSERVING, like some motor oils are. Those oils have friction modifiers that cause the clutch to slip and can cause big problems, so it is safer to stay away from regular motor oils for cars. The ATV oils are comparable in price if you shop around.
I am sure this is going to turn into the usual synthetic vs regular debate, but you should be fine with Yamalube. I actually bought the Kawasaki version of Yamalube because it came in a larger bottle and was more economical. The Yamaha dealer actually sold it to me! Some people say the synthetics are bad for ATV's others swear by them. I am sure they are probably fine, but I can't see the advantage of paying so much for an oil change. I've been using the ATV oil and so have my friends for years and its all good.
Jim