Yamaha blaster oil change question?

i need to change the oil in my 2004 blaster. is there a filter in it? ive heard no but i would think there should be something. i called a quad store and they said there is some type of spongy thing in it that you just clean out. is this right? how do you do it? also, how much oil do you put into it? one more thing. is it engine oil? some have said it does not need engine oil because it is 2stroke but i think it would need some. they say its fluid.