Both the "East" & "West" Career event's contain 8 different races.
You can obtain the achievement by playing on any difficulty, so you are fine to play on Rookie.
As the requirement is to place 3rd or better, you can just race through and as long as you win the majority of races, you should easily unlock the achievement.
You can try for the following achievement at the same time
There is however a Las Vegas track that is only available in the 17 race championship events.
So if you miss 1 win during this event, you can always pick it up during the championship event if you are going for the full 1000G.
I found that on Rookie difficulty, if I got to the front, I could avoid the snarl ups with AI and win without issue.
Sometimes I was knocked off quite early, but kept racing as I noticed that quite often the AI will be terrible in the last lap and as long as you are racing quickly, can make up lots of time and places.
As soon as you unlock any equipment for your vehicle, you can use the
to
Save Progress & Quit, then go to the
Customize Vehicle section and modify as required.
(In relation to that I found that everything except the chassis upgrade helped, when I added the chassis upgrade, I found the Vehicle a bit to twitchy in the air, but by all means try it yourself and see how you get on.)
The achievement pops at the end of the 8 races.