For me personally, 70 mph in an RC is just too darn fast. It doesn't matter how hood you are at driving, you're going to wrevk. And at those speeds, it's going to ne a very expensive wreck.
If you're going to get an Arrma, go 6s and up. Their 3s and 4s stuff isn't that great from my experience...
The Chinese brand RC's are not a good place for a novice to start monkeying around with. Since that is an all in one ESC/Receiver with a 5-wire servo, it will need a new motor, ESC, radio, and servo. And since you can't find hopup parts for most of the Chinese stuff, modding the car to use or...