Hello Paul
If you are intending to step into the nitro scene, perfer Tamiya and off roader essential, start off with the TNX.....its an off roader monster truck, 1/8 scale with a .18 OS engine that can hit 40+mph without modification....the only think is that its an RTR but the built is quite okay.
A standard radio will work with any nitro car as the basic functions are throttle, brakes, and steering. However, it will be good to invest in one better servo for the steering as the demands of off-road can be quite taxing.
What usually powers the servos is 4 AA batteries which is best stay with rechargables......they usually last quite afew runs before charging......best not to use disposable as the current may not be constant.......What is a good thing to buy in addition to what you have is a 'Fail Safe'....the function of this device is to return your throttle and steering back to original position...should your receiver batteries fail or some signal interference.
a full 125cc can last about 10 to 15 minutes depending on the type of engine and modifications you have done.
a 5 pot .21 Novarossi can hit off 60+ mph.....