If the car is truly autonomous and smart... It should be synchronized with your calendar and understand when it will not be needed. It is feasible that it will understand when it is time for an oil change.
This autonomous vehicle would then drive itself to the "maintenance station" where a specialized robot is waiting to remove the oil pan drain plug, remove the filter, drain the oil, and replace oil pan drain plug, then filter, then replace the oil. After this is complete the maintenance robot and your car will communicate and
confirm that everything is fine. If all is well the car continues on its way back to your house ready when you need it and your account is debited. If all is not well, then a human is summoned and and repair work can commence.
Moving even further forward. Computers have seen a trend where parts have become more modular and less proprietary. We will see the same in the automotive industry. Autonomous vehicles will force this. It is inevitable. Most certainly on mass production models. This will further make maintenance tasks and possibly even repair tasks manageable by a specialized robot in a "maintenance repair bay". Mechanics already utilize computers to diagnose automotive issues, balance tires, and a plethora of other tasks.
Does this remove the mechanics from the equation? I don't think on a higher level that it does. However on a low level maintenance task oriented mechanic, I believe it does. Further pointing to the automation issue that humanity will be soon be facing, many people will be unemployable through no fault of their own.