1) A brushless motor is "inside out" compared to your GWS motor. The windings are glued to the inside of the can, and the permanent magnets are bonded to the rotor. Since the wires don't move, you don't need brushes to transfer the electricity.
Take a look at the commutator on the GWS motor. It's cut into multiple sections. Depending on which two sections are in contact with the brushes at any given time, different sections of the windings are energized, creating the magnetic fields that push and/or pull against the fixed magnets in the can.
There are three wires coming from a brushless motor. Inside, all three wires are connected, and wound such that passing DC current through any two connections will create a magnetic field, making the rotor turn a partial revolution The computerized electronic speed control "commutates" a brushless motor by switching which two wires are being energized in a sequence.
Sensored and sensorless are two types of brushless motors. Sensored motors have a separate sensor, and an additional five wires, that tells the controller which direction and how fast the motor is turning. These are more complicated, more expensive, and difficult to reverse. They've pretty much gone the way of the dodo in R/C; only MaxCim still makes sensored brushless motors. SensorLESS motors use the fact that when a motor is coasting, it's generating electricity to see which direction and how fast the motor is turning. Knowing this information is crucial to making the motor turn in the correct direction, and knowing which two wires to pass current through at any given time to keep it turning in that direction. (from rcuniverse, Matt Kirsch)
2) The motor doesn't need to be messed around with, it would be best to run it softly for the first couple runs.
3) What do you like to do? Racing, bashing, mudding..