One thing to thing to think about is if your car can handle brushless at all. Brushless puts TONS of force on the components that were not designed to withstand a brushless motor. At a minimum, you will probably need to replace the clutch and gearbox with aluminum gears, and often times you will need to replace the driveshafts with aluminum as well. so that is just an extra cost to think about.
for your question on what motor to use, I would look if anyone has done this conversion to theirs, see what they used, and how it turned out. Also, I would recommend going with a more reputable brand if you can spare the cash. the components will be a lot more reliable, and you won't have to worry about your ESC quitting on you, or worse, catching fire.