I would not trust ANYONE to diddle with the idle mixture screw unless they were observing the duty cycle to be sure it is in the proper range. This procedure has been thoroughly outlined on this forum and many, including me, have run the test, so a pro should be able to do it too.
The 103 engine is known to require what some might consider to be excessive cranking to cold start or start and quit, requiring a second try. This is particularly noticeable in the summer when
"cold" starts are done at or near room temperature. The cold fuel calibration is lean at about 70F, because this is the cold start temp for emission certification. At colder temps, say 50 or below, the cold start behavior is usually much better.
The acculumator can be checked by installing a pressure gage and observing the behavior of the fuel pressure after shutdown. Assuming no external leaks, a rapid fall of pressure could be an indication of a malfunctioning fuel accumulator or an internal check valve.