I recently changed the gear oil in my rotary tiller and I simply used a hand pump. I imagine you can get them at Sears, local hardware store, etc. They also have electric ones out there.
Electric Oil Drain Pump
You should be more than fine with what you did. Next time, I would get a pump and simply stick a tube through the drain hole. The electric one is nice since you can move the tube around the gear box while it is pumping.
I imagine that you can get a similar O-ring from any local hardware store.
BTW, have you fixed your iMatch top link situation? Be careful about using it the way you had it. Nothing is preventing that top link from popping out during transport.
