please help lost oldboy brushless + esc's

[oldboy]

having not raced 1/10 buggys for many many years i was suprised and pleased when my younger son showed an interest so we have bought him a second hand b4.1 but then when delving deeper into the world of brushless i find that i am in totally over my head, could someone please explain what i should be looking for in a esc and a motor i have looked on ebay at the ezrun combos and the only bit of advice i have had is to go for a 60a one but there is so many other varients like number of turns for the motor, sensored or non sensored etc that i am totally lost. also when out with my losi with a older 40 hz transmitter the range seemed substantially further than my sons newer 2.4 ghz controller what sort of range should my son be getting. sorry for rambling on but if someone out ther could help i would be most grateful.