Excavators learn to repair a variety of power and parts, hydraulic systems and oil pumps. Depends on which one you studied. It takes at least 2 years to learn (only that the fur is not fine). You basically understand. It takes 6-7 years to become a master. Moreover, the repair of each component is different, and the repair machinery is different. Few repair shops repair all parts of excavators at the same time. Because of the large investment. They are all repaired by individual specialized parts. Unless it is a large-scale after-sales designated by the manufacturer.
As for opening a repair shop, it's up to you. There will be no less investment. It is best to have a large national project near your garage. Ongoing or about to go on. Your business will be much better that way. The economic profit of excavator maintenance is still good. As long as you have the funds to invest in the selected places. Excellent master skills. This is a very good industry.