With that being said, on some of the smaller cases (an oil change, or other simple repair) he allows his workers to complete those so he can have some "office" time. He can then work on the harder cases with his men or by himself. One of his men is also his son, as he clearly has indicated he is not a computer guy but knows that he needs one to run his business these days, so his son helps him more on that end of the business.
Now, with the non-"Open" hours, he spends some time at the beginning and end of the day to be able to complete business tasks and get them out of the way so that he can have that time with his customers and the vehicles.
On the other hand, I have a friend who also owns his own mechanic shop, and even though he has great experience and can work on the cars when needed, he likes being in the office and doing his tasks. Therefore, he has set up his shop so that he has plenty of staff to assist with the physical labor so that he can be in the office doing the other tasks required to run the business. but he can jump in and help out when needed, etc.
So, you have to decide what is important to you and it might take some time to get there, you may have to spend more time in the office to make things run properly until you get your business off the ground and running smoothly, and you might not be able to hire all of the staff needed to make sure that if you want to be working on the vehicles that you have someone who can be office staff, etc.
I hope this helps lead you to further discussions and thought.