With the single servo setup, it's really not much different. You remove one of the servos and the arm it used to use to connect to the steering rod (center of truck). You either cut off the un-used portion of the arm, or replace it with a ProLine arm. You also need to upgrade to the Traxxas Heavy Duty Servo Saver Spring.
There really isn't much to it....of course the 1 remaining servo needs to be upgraded to a stronger servo to do the job that 2 servos used to do.
Pretty basic upgrade. Doesn't matter which servo you remove either...pick your favorite.