You're in luck as I just remembered i've got my front tank out at the moment to clean the $**t out (no idea how i'm going to get it out but you can see how disgustingly black it is in the photo). Anyway if its the front tank you're pulling out, this is what it looks like - black part is the pump:
The pump just pulls upwards for removal.
Also while you're at it, if you look at the left of the pick you'll see a sort of funnel on top of the tank. This usually has a float valve in it so that the water can fill right up to the tank above the filler neck but they tend to get dirty too so you might want to pop it out and give that a quick clean too (just be sure not to loose it like i have lol)