In the end, the decision is yours. If you trust the seller's description, and truly believe the plane uses standard components, and you feel that the purchase is an acceptable risk, go ahead.

We're just trying to make sure you get started off on the right foot. Trying to go the cheap route rarely works out. Again, it's your decision.

The ads picture a standard Futaba Skysport 4 transmitter. If this is actually what is included with the plane, you probably get standard radio equipment. HOWEVER, he says nothing about frequency, so you'll have to ask. Frequencies need to be in the 72MHz band, and will be described by a channel number anywhere from 11 to 60. DO NOT buy if it's not in the 72MHz band. You cannot get the radio converted, and even if you could, it would've been cheaper to buy one outright.

As far as putting a smaller motor in it to make it easier to fly, it doesn't work that way. In fact, the motor power system this Jobar comes with may not be enough to fly it in the first place. Underpowering a plane rarely makes it easier to fly, unless you also signifigantly reduce the weight so it's a real floater. We don't know how much this one weighs, only that the whole package weighs about 2.5Kg, or about 5.5lb. If that's just the plane, it's a lead sled that will never fly.

I'm not sure where you get the idea that the AMA is some sort of governing body. The AMA's only limitation is that the plane weighs less than 55lbs, and that's only for insurance purposes. Otherwise, if it flies and isn't an obvious death missile waiting to happen (i.e. checked out to be safe), the AMA doesn't care.