They are also packaged in steps which correspond to the instructions so that parts are not mixed or lost during the assembly. Most first timers can assemble a kit in 4 to 8 hours. Any special tools needed are usually included in the kit, along with any special lubricants.
Electric cars are usually easier for beginner and are definitely less messy.
For all RTR cars which come with bushings, the addition of ball bearings is an easy way to reduce speed-robbing friction and get instant higher performance and longer run time. Most bearing sets cost between 20 and 40 dollars according to the car and how many bearings it needs. They are quieter, cleaner, and lighter. They are also easier to make run. As long as the batteries are charged and the wires are hooked up properly, the electric car will work.