Simply push the cover back in a bit, take a small screwdriver, or pointy tool and tap the key way.
It'll push inwards and off the shaft. Unless you really nail it, it should be re-usable.
It goes without saying, don't nick up the shaft, it'll damage the aluminum cover coming off (and going on) along with the seal..
Were taking a steel crank shaft spinning inside an ALUMINUM cover..
I'd sand / wire brush that exposed crankshaft MORE till it shines super clean. You don't want any rust debris there and the cover will come off much easier..
Your almost there!
Oops, didn't see page two.. Yep, it'll pop out.. Wire brush clean to later re-install...