In rc cars, ''kori'' means the body of the car, usually the LEXAN body.
The servo seems to be 2,8kg if my calculations are correct, i think thats quite a small amount of torque for a FOFF car, since bms-630 has about 15kg.
You dont have to start with a 2,4ghz radio, almost any radio will do at the start.
I don't know much about wheelwideners, we just have to wait for someone to answer to that.