That pump thingo probably bolts onto the crankcase cover with 4 bolts. They usually do. That worm gear in there will most likely be held on with a key and bolt on the end. Its fricken rusty so its gonna be an *** to get off. If u dont have a puller then heat to the rescue. That worm gear will have to come off first and then the metal outer casing should just come off once u undo the 4 bolts. The bolts may be behind the worm gear so if u can see em then dont stress. If its not bolted on then just cut it off with a cut off wheel. It looks to me as if its a 3/4" keyed shaft but i could be wrong. If that worm gear is cast which is most likely is, they crack real easy so dont bash it to hard. Also, if ur bashing down on the crank then put something like a block of steel or a hammer under it to support the shaft so it doesnt bend. Nothing worse then a bendy shaft! XD