Is it reasonable to attempt to troubleshoot a customer’s weapon without being able to fix the parts?

Though I believe it is necessary to be able to fix fasteners and other small parts, I also believe it is reasonable to begin the trouble shooting process even if you are unable to fix the part causing the problem. Step one is always clearing the firearm and if the customer was claiming it wont chamber a round and you find out it was because they were loading them backwards, then problem solved. You did not need the ability to fix small parts to solve this problem. Most of the time you will not have the small part that has broken on hand anyway so why not begin the process to at least identify the issue component. Now if the part in question is not fully broken and you are able to fix the part to get the firearm working again then awesome, but you will never get to that point in the process until you make the attempt. Recently I was given a 1911 with a removable front sight. The client was getting older and wanted Tru Glow sights put on so he could see it better. This is usually a few minutes of work with double that going into making sure they are lined up correctly. However, The front sight I was provided was not made for that make and model firearm. It was my ability to use files correctly to reshape the sight to fit that allowed me to see the job to completion. However, there is no shame in turning down work because you are not comfortable attempting something your uncomfortable or unconfident with. I did it for years before I had the confidence to try more stuff.