I am a big fan of supporting your LHS. Can they order it for you? If not, I would just order it online.

After looking at the specs of the plane, a 91 4-stroke might be a better idea. Because of the extra drag in the water, you may need that extra power to get on plane. Just get a good match with your prop size and pitch.

As for radios, everyone have a personal favorite. In my opinion, you cannot go wrong with either a Futaba or JR radio. Both have buddy box plugs. I would go no less that a 6 channel system in case you add flaperons or expand you airplane fleet at some point. Personally I have a Futaba. Guys in my club are diehards on either side. Each has their own good features and drawbacks. You just have to weigh the pros and cons to determine which you prefer.