rustler/stampede question

i am modifying my traxxas rustler into a stampede, nothing stock except motor and electronics....... anysuggestions on what else i need to change? frank at maxxfusion told me to get a new steering servo, but which one.....
also i want to switch to a brushless setup, what would be a good combo for a descent price range,,,

please help, im new to this, getting out of motocross for my son's sake, too dangerous, long story.....