It depends on what needs to be done, but most procedures require two hands with a minimum of two fingers on each one. 20/60 eyesight or better is an advantage.

The exhaust gas recirculation, (EGR) is a system that includes a valve, a sensor, and various passages. Part of that system is monitored by the Engine Computer so your mechanic will need a scanner to erase any diagnostic fault codes when he's done. Those codes also tell him which circuit or system needs further diagnosis. Fault codes never say to replace parts. Every shop has a number of scanners that will work with your car. Many mechanics even have their own scanners since they are almost always in use by someone.