Im not sure on what the older gq's tranny looks like, but the auto in mine gu (i think they are very similar) the filter is a flat metal filter, right in the middle. it has 4 or 5 bolts holding it in from memory.
Keep in mind that when you changed your oil you only changed about 50%. the reason being the majority of the oil is in the torque converter and doesnt get released unless you remove the converter, which requires removing the enitre box. Dont get me wrong, if your oil was cactus the change will be good for it. The auto takes about 12L of oil from dry, and i would assume you took out about 5-6L, better then no change, but still pays to get it done by a pro.